Add diagram workbench UI with Modelica DoF coaching and ISO glyphs.

Ship the Next.js cycle editor with CAD chrome, technical HX symbols, Fixed/Free boundary guidance, and secondary water/air pressure drop support in the solver stack.

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

apps/web/public/docs/components/heat-exchanger-generic.md

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+# HeatExchanger (generic)
+
+Config type: `"HeatExchanger"`  
+Source: `crates/components/src/heat_exchanger/exchanger.rs` + ε-NTU / LMTD models
+
+---
+
+## EN
+
+### Purpose & model
+
+Generic two-stream HX with selectable model:
+
+- **ε-NTU** effectiveness  
+- **LMTD** / counterflow forms  
+
+Ports: hot_in/out, cold_in/out (Modelica-style 4-port).
+
+```
+NTU = UA / C_min
+ε = f(NTU, C_r, flow arrangement)
+Q = ε · C_min · (T_hot,in − T_cold,in)
+```
+
+**Requires live four-port edge state** for residual evaluation on the generic path — inlet-only scalar BCs do not invent outlet states.
+
+### Residuals & `n_equations()`
+
+Inner model residual count (often 2–3 per side balance depending on configuration).
+
+### Ports
+
+| Port | Role |
+|------|------|
+| `hot_inlet` / `hot_outlet` | hot stream |
+| `cold_inlet` / `cold_outlet` | cold stream |
+
+### Calibration
+
+`z_ua` on UA (default 1.0).
+
+### When not to use
+
+For refrigeration condensers/evaporators prefer specialized `Condenser` / `Evaporator` / `FloodedEvaporator` / BPHX which know phase-change ε-NTU and secondary dual modes.
+
+---
+
+## FR
+
+### But
+
+Échangeur **générique** 4 ports (ε-NTU / LMTD).
+
+### Attention
+
+Exige un état **4 ports live**. Pour frigo, préférer Condenser / Evaporator / Flooded / BPHX.
+
+### Calibration
+
+Z_UA = 1 par défaut.