Snapshot WIP: solver HP epic progress, BPHX/HX physics, BMAD skill refresh.

Capture uncommitted solver robustness work (regularization, domain errors, linear solver lifecycle, tube DP/MSH), web workbench updates, and synced BMAD skills across IDE agent folders before starting BPHX pressure-drop.

Co-authored-by: Cursor <cursoragent@cursor.com>

HANDOFF.md

@@ -0,0 +1,372 @@
+# Entropyk — Development Handoff
+
+> **Purpose.** This document hands off the current state of Entropyk to a new
+> coding tool / session. It summarizes **what was done**, **why it was done that
+> way** (key technical decisions), and **what remains to do**, so work can resume
+> without loss of context.
+>
+> **Conventions (from `AGENTS.md`).** Communicate with the user (**Sepehr**) in
+> **French**; write all code / docs / commit messages in **English**. Rust package
+> manager = **cargo**; Python = **uv** (venv at repo-root `.venv`).
+>
+> **Last updated:** 2026-07-07
+
+---
+
+## 1. Project overview
+
+**Entropyk** is a Rust steady-state thermodynamic-cycle simulation library for
+refrigeration, heat pumps and HVAC. The goal (Sepehr's) is to make it a
+best-in-class HVAC **design + control** simulator — **very accurate and very
+fast** — to replace an internal tool. Hard rule from the user: **no "bricolage"**
+(no hacks such as auto-injecting design-point temperatures). Every model must be
+**genuinely physically coupled** and must **respect the First Law**.
+
+### Workspace layout
+
+```
+entropyk/
+├── crates/
+│   ├── core/          # Strong types (Pressure, Temperature, Enthalpy…), smoothing primitives
+│   ├── components/    # Thermodynamic components (Compressor, HX, valves, ReversingValve…)
+│   ├── fluids/        # Fluid backends (CoolProp, tabular, incompressible)
+│   ├── solver/        # Newton-Raphson / Picard / Homotopy, System topology, DoF, controls
+│   ├── entropyk/      # Main library facade (System, SystemBuilder, rating)
+│   ├── cli/           # CLI: run / qualify / rate / scop / seer commands
+│   ├── vendors/       # Vendor data parsers
+│   └── bindings/      # Python (PyO3), C (cbindgen), WASM  — DO NOT build in this env
+├── apps/web/          # Dymola-style web UI (SvelteKit + Vitest)
+├── _bmad/ , _bmad-output/   # BMAD methodology workflows + artifacts
+└── AGENTS.md          # Project instructions (READ FIRST)
+```
+
+---
+
+## 2. What has been DONE (verified)
+
+### 2.1 Genuine secondary-side coupling of heat exchangers (ε-NTU)
+The core goal: HX respond to **secondary** (water / brine / air) temperature & flow.
+- `Condenser`, `Evaporator` and `FloodedEvaporator` brought to the same coupled
+  ε-NTU level. Secondary fields (`secondary_inlet_temp_k`, `secondary_capacity_rate`),
+  builders `with_secondary_stream` / `set_secondary_stream`, helpers `coupled_ready`,
+  `coupled_duty`, `effectiveness`, `cond_temperature` / `evap_temperature`.
+- Coupled residual path active only when a secondary stream is set AND indices
+  resolved AND P_in > 10 kPa (otherwise legacy path — **backward compatible, DoF
+  unchanged**). `Q = ε·C_sec·ΔT`, `ε = 1 − exp(−UA/C_sec)` (C_min = C_sec for a
+  phase-changing refrigerant). Analytical Jacobian (dT/dP via central FD).
+- Files: `crates/components/src/heat_exchanger/{condenser,evaporator}.rs`.
+
+### 2.2 Emergent pressures (end-to-end coupling) — the "vrais modèles échangeurs" epic
+Condensing / evaporating **pressures are now emergent** from the HX↔secondary
+balance instead of fixed by compressor design points. Opt-in `emergent_pressure`
+mode on each component:
+- **Compressor** (`comp-emergent`): mass-flow closure `ṁ = ρ_suc·V_s·N·η_vol`;
+  r0 = ṁ_state − ṁ_calc.
+- **Condenser** (`cond-emergent`) / **Evaporator** (`evap-emergent`): 3 thermo eqs
+  (ΔP, energy balance, outlet closure), `n_equations` +1.
+- **EXV** (`exv-emergent`): drops the P_evap fix, keeps only isenthalpic h3=h2,
+  `n_equations` −1.
+- Integration test: 4-component emergent loop converges; varying secondary T/flow
+  changes COP/capacity; **DoF balanced (9=9)**.
+
+### 2.3 Modular control architecture (arch-1 … arch-6) — ALL DONE
+- **arch-1** Saturated-PI controller wired into System DoF (2 residuals + 2 unknowns
+  per loop; actuator u → CalibIndices, measurement y ← measure_output; co-solved).
+- **arch-2** Typed ports `PortKind{Refrigerant, Secondary, Mechanical, Signal}` +
+  edge validation by kind; Signal ports for control wiring.
+- **arch-3** `controls[]` schema + control-block library (Min/Max/Setpoint/Limiter),
+  CLI design/control command co-solving design + control.
+- **arch-4** subsystems/instances hierarchical templates (reusable parameterized
+  assemblies flattened to graph; multi-circuit A/B).
+- **arch-5** unified model IR across CLI / Python / WASM / UI (schema v2 loader,
+  v1-compatible).
+- **arch-6** **Physical actuators — all 6 done**, each with exact analytic Jacobian
+  (FD only for property derivatives) and CLI wiring + example + integration test:
+  1. **EXV orifice** — `ṁ = Cd·A(θ)·√(2ρΔP)`, opening as bounded solver var.
+  2. **Fan head-pressure** — air-cooled condenser: secondary air capacity rate scales
+     with fan speed; fan speed controls condensing pressure. `UA_eff=(1−λ)·UA_nom`.
+  3. **Slide-valve** (screw compressor) — capacity modulation of swept volume.
+  4. **Liquid-injection** EXV — economized screw, controls discharge temperature
+     (factor-actuator: closed by a `controls[]` loop, does NOT grow `n_equations`).
+  5. **Flooded-condenser level** (`cond-level`) — head-pressure via liquid level;
+     mirrors the fan actuator, mutually exclusive with it (shares `fan_actuator_idx`).
+     Exact flood Jacobian `∂r1/∂λ = +UA_nom·(T_cond−T_sec)·exp(−UA_eff/C_sec)`.
+  6. **Four-way reversing valve** — see §2.6.
+- **p0a** real constraint measurement via fluid backend (removed mocked
+  superheat / subcooling / capacity in `system.rs`).
+- **p0b** compressor variable-speed capacity actuator (bounded `speed_hz` DoF).
+
+### 2.4 Modular seasonal rating (SEER / SCOP / IPLV / NPLV / ESEER) — DONE
+Per Sepehr's request that **the standards be swappable when norms change**:
+- `rate.rs` — AHRI 550/590 IPLV/NPLV/ESEER: re-solve base scenario at each part-load
+  point overriding secondary temps + compressor speed; rayon-parallel points.
+- `seasonal.rs` — EN 14825 bin method (SCOP/SEER): per-bin coupled re-solve driven by
+  outdoor temp, linear building load line, Cd cycling degradation, backup heater.
+  **Modular climate selection** (`BinClimateStandard`) so climates/standards are
+  pluggable.
+- CLI subcommands `rate`, `scop`, `seer` + example configs + unit & integration tests.
+- French `CLI_TUTORIAL` section for these commands.
+- **Full documentation written** (per user request).
+
+### 2.5 Circuit on/off staging — DONE
+- `CircuitConfig.enabled: bool` (`#[serde(default = "default_true")]`) in
+  `crates/cli/src/config.rs`. A disabled circuit's components / edges / thermal
+  couplings are **never added to the `System`** → excluded from the solve entirely
+  (zero mass flow / duty). Physically-correct steady-state for an unenergized
+  circuit, **not** a hack.
+- 5 circuit-iteration loops in `run.rs` skip-guarded; all-disabled → early rejection.
+- Example `chiller_r134a_dual_circuit_staging.json`. Verified e2e: both on = 15.139 kW
+  / COP 4.379 (8 edges); circuit B off = 7.569 kW (4 edges) = exactly half.
+- 2 CLI integration tests pass.
+- NOTE: the component-level `OperationalState{On,Off,Bypass}` in
+  `state_machine.rs` exists but is **dead code w.r.t. the solver** — staging is done
+  at CLI/config level, not via that enum.
+
+### 2.6 Four-way reversing valve (arch-6 #6) — DONE
+- `crates/components/src/reversing_valve.rs`: `ReversingValve` + `ReversingMode{Cooling,
+  Heating}`. Deterministic inline 2-port pass-through:
+  - r0 = P_out − (P_in − ΔP), `ΔP = ΔP_base + k·ṁ·|ṁ|`
+  - r1 = h_out − (h_in + Δh_leak)
+  - r2 = ṁ_out − ṁ_in (dropped when the inlet/outlet share a mass-flow index)
+  - `n_equations` = 2 or 3. Exact analytic Jacobian (`∂ΔP/∂ṁ = k·2|ṁ|`).
+  - **DoF-neutral**: emits a pressure *relation* (not a fix), so it works unchanged
+    in both fixed-pressure and emergent-pressure cycles.
+- **Key modeling decision (honest, no bricolage):** the validated cycle uses
+  `Δh_leak = 0` (**isenthalpic ΔP-only**). A non-zero single-stream leak enthalpy
+  injects `ṁ·Δh_leak` with **no matching source** → it broke machine-level First Law
+  (measured 0.077 kW imbalance, wrong sign on the discharge line). The rigorous
+  discharge→suction leak needs a **bypass-mass split (two streams)** — deferred to a
+  future topology layer. The ΔP alone (~0.25 bar valve-body drop) already reproduces
+  the cited ~1–3 % COP/capacity penalty **and closes the First Law exactly**. The
+  `leak_enthalpy` parameter is retained + documented for the future bypass-mass model.
+- CLI arm `"ReversingValve" | "FourWayValve"`. Example
+  `heatpump_r410a_reversing_valve.json` (reversible R410A air→water HP, heating mode,
+  RV on discharge line, all emergent). **Verified e2e:** converges 5 iters, ΔP
+  39.068 → 38.788 bar, Q_cool 9.918 kW / Q_heat 15.486 kW / Power 5.491 kW, EER 1.806,
+  First Law closes. 5 unit tests + 1 CLI integration test
+  (`test_reversing_valve_imposes_pressure_drop_penalty`).
+
+### 2.7 Fluids accuracy fix — DONE
+- `entropyk-fluids :: tabular_backend::tests::test_tabular_vs_coolprop_accuracy` was
+  failing (embedded `r134a.json` density >1 % off vs CoolProp). Fixed **properly** by
+  regenerating the table from CoolProp (not by widening epsilon).
+
+### 2.8 Web UI (apps/web) — DONE (earlier turns)
+- Secondary ports (`secondary_inlet` / `secondary_outlet`, labeled htf·in / htf·out)
+  on all HX; `resolveSecondaryStreams` maps a connected boundary source into HX
+  secondary params and hides secondary edges from the solver graph.
+- Dymola-style light UI, grid snap, node rotation. Vitest suite green (61 tests).
+
+### 2.9 Workspace warning cleanup — 0 warnings
+- `cargo build --workspace --all-targets` (bindings excluded) emits **0 warnings**.
+- Notable real fix: `crates/components/src/brine_boundary.rs` `mod tests` was missing
+  `#[cfg(test)]` (compiled into normal builds). Migrated deprecated
+  `TEMP_MASS_FLOW_SEED_KG_S` → `DEFAULT_MASS_FLOW_SEED_KG_S` across 8 solver test files.
+
+---
+
+## 3. Key technical patterns & conventions (carry these forward)
+
+- **Free-actuator DoF pattern**: +1 unknown appended at the END of the state vector.
+  *Setpoint* actuators (slide / fan / cond-level) grow `n_equations()` by 1; *factor*
+  actuators (liquid-injection) do NOT — a `controls[]` loop closes them.
+- **Two Component conventions coexist**:
+  - *Port-based* (e.g. `ExpansionValve<Connected>` reads `self.port_inlet`).
+  - *Index-based* (`IsenthalpicExpansionValve`, `Condenser`, `ReversingValve`):
+    `set_system_context(offset, &[(m_idx,p_idx,h_idx); edges])`, edge[0]=inlet,
+    edge[1]=outlet, then reads `state[idx]`. **The emergent CLI cycle uses the
+    index-based convention.** `IsenthalpicExpansionValve` is the template for new
+    inline components (its `get_ports()` returns `&[]`).
+- **`same_branch_m`**: true when inlet_m_idx == outlet_m_idx (series-branch collapse,
+  CM1.4) → drop the mass-conservation residual.
+- **Jacobian policy**: exact analytic required. FD allowed ONLY for property
+  derivatives (dT/dP, dρ/dP). Never numerical-diff a whole residual.
+- **Emergent vs fixed pressure**: emit pressure *relations* (ΔP), not absolute
+  pressure *fixes*, to stay DoF-neutral across both topologies.
+- **First Law is a hard gate**: `System::cycle_performance` sums every component's
+  `energy_transfers`; any unsourced enthalpy injection breaks closure. Do not add
+  energy without a physical source (this is what killed the leak-enthalpy model).
+- **Smoothing**: use `entropyk_core::smoothing` (smoothstep, smootherstep,
+  cubic/quintic_blend, smooth_max/min/abs/clamp) for C¹/C² correlation transitions —
+  never ad-hoc `if`/`tanh` — to keep the Newton Jacobian continuous.
+- **CRLF gotcha**: example JSONs are written with CRLF on Windows; test string-patches
+  using `\n` fail silently. Split on a distinctive marker (e.g. `"Circuit B"`) then
+  `replacen`.
+- **`edit` tool gotcha**: verify match-arm headers (`"Pipe" => {`) survive edits;
+  re-view files after risky edits.
+- **AGENTS.md integration protocol**: a new component must be integrated across Rust
+  core+solver, CLI, Python (PyO3), and WASM. Several new components currently have
+  Rust core + CLI only (bindings pending — see §5).
+
+---
+
+## 4. Build / test / run
+
+```bash
+# Build & test core crates (bindings excluded — they DON'T build in this env)
+cargo build --workspace --all-targets --exclude entropyk-python --exclude entropyk-c --exclude entropyk-wasm
+cargo test  -p entropyk-core -p entropyk-components -p entropyk-solver -p entropyk-cli -p entropyk
+
+# Targeted (fast) examples
+cargo test -p entropyk-components reversing_valve
+cargo test -p entropyk-cli --test single_run test_reversing_valve_imposes_pressure_drop_penalty
+cargo run  -q -p entropyk-cli -- run --config crates/cli/examples/heatpump_r410a_reversing_valve.json
+
+# Frontend
+cd apps/web && npm run test        # Vitest
+cd apps/web && npm run dev         # http://localhost:3000
+cargo run --package entropyk-demo --bin ui-server   # backend http://localhost:3030
+
+# Python bindings (uv only — never pip)
+uv run maturin develop --release
+uv run pytest crates/bindings/python/tests/
+```
+
+**Guardrails:** NEVER `cargo test --workspace` (pyo3 fails on Python 3.14). CLI
+integration tests are slow (~1–2 min each, real CoolProp solve) and self-skip when
+CoolProp is unavailable (`if status != Converged { return; }`). `cargo test` accepts
+only ONE positional TESTNAME filter per invocation.
+
+---
+
+## 5. What REMAINS to do (prioritized)
+
+### 5.1 In progress / immediate
+- **`adv-override-control`** *(DONE 2026-07-07)* — Modelica-style **override/selector
+  control** + **offset-free** saturated-PI. (1) Fixed the control law to the
+  canonical offset-free form `r_y = K(y_ref−y) − (x − S(x))` (was `x + S(x)`, a
+  droop with steady-state offset that forced fragile high gains → the reported
+  convergence/slowness). (2) New `inverse/override_network.rs`: one actuator
+  arbitrated by several `Objective{output,setpoint,gain,combine:min|max}` folded
+  through C^∞ `softMin/softMax` with **exact analytic selector weights** (Jacobian-
+  smoothing; literature-backed robustness). (3) `SaturatedController` gains opt-in
+  `objectives`+`alpha`; `system.rs` residual/Jacobian branch for network mode
+  (`∂E/∂col = Σ w_i(−gain_i)∂y_i/∂col`). (4) Config `controls[].objectives[]`+`alpha`
+  (schema-exposed), `run.rs` wiring. Example `chiller_r134a_exv_override.json`;
+  unit + FD-Jacobian + CLI integration tests (286 solver tests pass). Spec:
+  `_bmad-output/implementation-artifacts/spec-advanced-override-control.md`.
+  ROBUSTNESS (done): warm-started **ADAPTIVE activation continuation**
+  (`SaturatedController::activation` λ walked 0→1 by `run.rs`: primary-only
+  baseline → full network). The λ-step now uses the **same predictor–corrector
+  control as `strategies::homotopy`** — start 0.5, **halve on any failed solve**
+  (retry from the last good λ), grow on success, floor `MIN_LAMBDA_STEP=5e-3` —
+  so the walk auto-refines through the hard switching region and takes big steps
+  elsewhere; each step is seeded from the previous solution. CLI also wires
+  `solver.max_iterations`/`tolerance` into every solver stage (was capped at 100).
+  Measured effect: markedly wider convergence range vs the old fixed `[0,0.5,1]`
+  schedule (aggressive EXV overrides now converge through many more intermediate
+  λ). Known **physical** limit (not a solver defect): with a `superheat_regulated`
+  evaporator and the EXV opening as the *only* actuator, forcing capacity well
+  below the natural duty drives `∂capacity/∂opening → 0` → the plant Jacobian goes
+  singular (loss of controllability). The robust demonstrated path uses a
+  well-conditioned actuator (compressor `f_m`), covered by the passing test
+  `test_override_capacity_limit_takes_authority_via_continuation`.
+  NEXT (optional): a second actuator (e.g. compressor speed) to restore
+  controllability for deep EXV duty cuts; optional setpoint **scheduling**
+  (`Table1D/2D`/`Poly`) per the PPTX/CombiTable patterns.
+- **`p0b-exv-opening`** *(DONE 2026-07-07)* — controllable EXV opening regulates
+  evaporator **superheat**. Evaporator gains an opt-in `superheat_regulated` mode
+  (drops the emergent outlet-closure `r2` → superheat emerges from the ε-NTU energy
+  balance); a `controls[]` saturated loop with `actuator.factor:"opening"` drives the
+  opening (wired to `CalibIndices.actuator`), the EXV orifice residual closes it, DoF
+  stays square (orifice +1, drop r2 −1, saturated +2/+2). Real `measure_output(Superheat)`
+  added. Example `chiller_r134a_superheat_control.json`, integration + unit tests, +
+  fail-fast config guards. Spec: `_bmad-output/implementation-artifacts/spec-p0b-exv-opening.md`.
+- **`p0c-json-schema`** *(LARGELY DONE — audit before extending)* — the CLI `schema`
+  command already emits the canonical Model IR JSON Schema (`emit_schema` →
+  `ScenarioConfig::json_schema()` via `schemars`); `controls[]` (saturated loops) parse
+  and co-solve; bounded control variables are expressed in `actuator{initial,min,max}`;
+  `parse_component_output` supports capacity/superheat/subcooling/saturationTemperature/
+  massflow/pressure/temperature. REMAINING (optional): a dedicated top-level hard-inverse
+  `constraints[]` array + a distinct `design`/`control` CLI command (today `run` co-solves
+  everything).
+- **`p0c-ui-align`** — make the control schema map cleanly to the `apps/web`
+  node/port model so the UI can generate/consume it. **(User note: a UI is being
+  developed in parallel — keep schema UI-friendly.)**
+- **`p0-tests-docs`** — unit + integration tests proving control actually regulates
+  (varying target changes state physically); update docs.
+
+### 5.2 Bindings (AGENTS.md protocol — currently Rust+CLI only)
+- **Python (PyO3) + WASM** wrappers for the new components/actuators, notably
+  `ReversingValve`, flooded-level, slide-valve, liquid-injection.
+  - ⚠️ **Blocked in this env**: PyO3 max supported Python is 3.13 but the interpreter
+    is 3.14. Fix by upgrading `pyo3` in `crates/bindings/python` OR pinning the uv env
+    to 3.13, then verify `uv run maturin develop --release` + `uv run pytest`. The
+    bindings crates may be absent from the current snapshot — confirm before starting.
+
+### 5.3 Water-cooled machines (workspace `61XW_VFD_EMEA`, `30XF`, `61AQ` references)
+- **`wc-single-circuit-e2e`** — compressor + condenser + EXV + flooded-evap with water
+  loops both sides; validate convergence + secondary sensitivity. *Easiest first-class
+  target (no air/fan/defrost).*
+- **`wc-multicircuit`** — parallel dual-circuit (A/B) compressors/HX with a shared
+  secondary manifold (`System_2C`).
+- **`wc-pass-count`** — 1P/2P/3P evaporator & condenser pass configuration.
+- **`wc-slide-valve`** — second actuator alongside speed (`CompressorControl_double`).
+  *(A screw slide-valve actuator already exists — this is the water-cooled twin-actuator
+  variant.)*
+- **`exv-sst-actuator`** — make EXV opening physically move suction saturated temp /
+  mass flow so a SaturatedController can regulate SST.
+
+### 5.4 Real-machine feature blocks (30XF / 61AQ parity)
+- **`rm-staging`** — 1–4 module staging state machine (61AQ `StateMachine`). *(Circuit
+  on/off staging at config level is done; this is the multi-module controller.)*
+- **`rm-fan-headp`** — air-cooled condenser SDT limit → fan speed via SaturatedController.
+  *(A fan head-pressure actuator exists — this is the closed-loop controller variant.)*
+- **`rm-exv-orifice`** — `ṁ=Cd·A(θ)·√(2ρΔP)` opening sets emergent P_evap=SST (matches
+  61AQ `EXVControl_cooling`). *(Orifice actuator exists — this is the SST loop.)*
+- **`rm-freecool`** — free-cooling exchanger + glycol routing + OAT changeover (30XF).
+- **`rm-defrost`** — defrost seasonal correction block (`Auxiliary.Defrost.Defrost_factor`).
+- **`rm-en14511`** — EN 14511 net-from-gross corrections (pump/fan penalties on net
+  capacity/power).
+- **`rm-moistair`** — moist-air (RH / wet-bulb) psychrometric properties for air-side HX.
+- **`rm-surrogate`** — MCHX/compressor surrogate-map (performance-map) backend for HX
+  and compressor (speed/accuracy trade-off).
+
+### 5.5 Web UI
+- Circuit **`enabled` toggle** in `apps/web` configBuilder (emit `"enabled": false`).
+- Keep the control JSON schema aligned with the UI node/port model (see `p0c-ui-align`).
+
+### 5.6 Bigger / architectural (research-backed)
+- Consider a **modular Modelica-style** model/controller composition system (user's
+  explicit interest) — arch-1…6 laid the groundwork (typed ports, subsystems, unified
+  IR, controls[]); next is a first-class reusable controller/model library and
+  possibly acausal connectors.
+- Performance: exploit `research-improve` findings (surrogate maps, warm-starting,
+  Anderson acceleration already present, parallel rating points already via rayon).
+
+---
+
+## 6. Known environment limitations
+- **Python bindings do not build here**: PyO3 max 3.13 vs interpreter 3.14.
+- **`cargo test --workspace` fails** for the same reason — test crates individually.
+- CoolProp is enabled via Cargo features; CLI/solver runs need **no** `--features`
+  flag. CLI integration tests self-skip without CoolProp.
+
+---
+
+## 7. Key files map
+| Area | Path |
+| --- | --- |
+| Project instructions | `AGENTS.md` |
+| Coupled HX | `crates/components/src/heat_exchanger/{condenser,evaporator,flooded_evaporator}.rs` |
+| Reversing valve | `crates/components/src/reversing_valve.rs` |
+| Inline-component template | `crates/components/src/isenthalpic_expansion_valve.rs` |
+| Compressor + actuators | `crates/components/src/isentropic_compressor.rs` |
+| System / DoF / performance | `crates/solver/src/system.rs` |
+| Controls / saturated PI | `crates/solver/src/inverse/saturated_control.rs` |
+| Smoothing primitives | `crates/core/src/smoothing.rs` |
+| CLI wiring hub | `crates/cli/src/run.rs` |
+| CLI config schema | `crates/cli/src/config.rs` |
+| Rating / seasonal | `crates/cli/src/{rate,seasonal,qualify}.rs` |
+| CLI integration tests | `crates/cli/tests/single_run.rs` |
+| Examples | `crates/cli/examples/*.json` |
+| Web UI | `apps/web/src/lib/{componentMeta,configBuilder}.ts` |
+| Session artifacts | `_bmad-output/implementation-artifacts/sprint-status.yaml` |
+
+---
+
+## 8. Test status snapshot (at handoff)
+- **PASS**: entropyk-core, entropyk-components (792), entropyk-solver (+integration),
+  entropyk, entropyk-cli, web vitest (61). **0 warnings** on core crates.
+- **Fixed**: `entropyk-fluids` tabular-accuracy test (regenerated r134a.json).
+- **Not buildable in this env**: `bindings/python` (PyO3 vs Python 3.14).