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>

crates/solver/tests/common/mod.rs

@@ -0,0 +1,111 @@
+//! Shared helpers for the `entropyk-solver` Phase-0 integration tests.
+//!
+//! Provides the three reference emergent-pressure R134a cycles used as the
+//! Phase-0 golden safety net. The construction mirrors `benches/common.rs`
+//! so benchmarks and regression tests stay aligned.
+
+use std::sync::Arc;
+
+use entropyk_components::{Condenser, Evaporator, IsenthalpicExpansionValve, IsentropicCompressor};
+use entropyk_fluids::{CoolPropBackend, FluidBackend};
+use entropyk_solver::system::System;
+use entropyk_solver::{ConvergedState, FallbackConfig, FallbackSolver, NewtonConfig, Solver};
+
+fn coolprop_backend() -> Arc<dyn FluidBackend> {
+    Arc::new(CoolPropBackend::new())
+}
+
+fn build_emergent_cycle(
+    cond_sec_temp_k: f64,
+    evap_sec_temp_k: f64,
+    ua_cond: f64,
+    ua_evap: f64,
+) -> System {
+    use entropyk_components::isentropic_compressor::VolumetricEfficiency;
+
+    let backend = coolprop_backend();
+    let fluid = "R134a";
+
+    let comp = Box::new(
+        IsentropicCompressor::new(0.70, 318.15, 278.15, 5.0)
+            .with_refrigerant(fluid)
+            .with_fluid_backend(backend.clone())
+            .with_displacement(6.5e-5, 50.0, VolumetricEfficiency::Constant(0.92)),
+    );
+
+    let cond = Box::new(
+        Condenser::new(ua_cond)
+            .with_refrigerant(fluid)
+            .with_fluid_backend(backend.clone())
+            .with_secondary_stream(cond_sec_temp_k, 1500.0)
+            .with_emergent_pressure(5.0),
+    );
+
+    let exv = Box::new(
+        IsenthalpicExpansionValve::new(278.15)
+            .with_refrigerant(fluid)
+            .with_fluid_backend(backend.clone())
+            .with_emergent_pressure(),
+    );
+
+    let evap = Box::new(
+        Evaporator::new(ua_evap)
+            .with_refrigerant(fluid)
+            .with_fluid_backend(backend.clone())
+            .with_secondary_stream(evap_sec_temp_k, 2000.0)
+            .with_emergent_pressure(),
+    );
+
+    let mut system = System::new();
+    let n_comp = system.add_component(comp);
+    let n_cond = system.add_component(cond);
+    let n_exv = system.add_component(exv);
+    let n_evap = system.add_component(evap);
+
+    system.add_edge(n_comp, n_cond).unwrap();
+    system.add_edge(n_cond, n_exv).unwrap();
+    system.add_edge(n_exv, n_evap).unwrap();
+    system.add_edge(n_evap, n_comp).unwrap();
+
+    system.finalize().unwrap();
+    system
+}
+
+pub fn build_reference_cycle_a() -> System {
+    build_emergent_cycle(303.15, 285.15, 766.0, 1468.0)
+}
+
+pub fn build_reference_cycle_b() -> System {
+    build_emergent_cycle(313.15, 283.15, 900.0, 1600.0)
+}
+
+pub fn build_reference_cycle_c() -> System {
+    build_emergent_cycle(308.15, 291.15, 850.0, 1800.0)
+}
+
+fn newton_config_for_reference() -> NewtonConfig {
+    let initial_state = vec![
+        0.05,   // shared mass flow [kg/s]
+        11.6e5, // comp->cond pressure [Pa]
+        445e3,  // comp->cond enthalpy [J/kg]
+        11.6e5, // cond->exv pressure [Pa]
+        262e3,  // cond->exv enthalpy [J/kg]
+        3.5e5,  // exv->evap pressure [Pa]
+        262e3,  // exv->evap enthalpy [J/kg]
+        3.5e5,  // evap->comp pressure [Pa]
+        405e3,  // evap->comp enthalpy [J/kg]
+    ];
+    NewtonConfig {
+        max_iterations: 200,
+        tolerance: 1e-6,
+        initial_state: Some(initial_state),
+        ..NewtonConfig::default()
+    }
+}
+
+/// Solves a reference cycle and returns the converged state vector.
+pub fn solve_reference_system_with_state(system: &mut System) -> ConvergedState {
+    let newton = newton_config_for_reference();
+    let mut solver = FallbackSolver::new(FallbackConfig::default()).with_newton_config(newton);
+    solver.solve(system).expect("reference cycle must converge")
+}