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/flow-merger.md

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+# FlowMerger
+
+Config type: `"FlowMerger"`  
+Source: `crates/components/src/flow_merger.rs`
+
+---
+
+## EN
+
+### Purpose & model
+
+**N inlets → one outlet**. Mass and energy mix at common pressure:
+
+```
+ṁ_out = Σ ṁ_in,i
+ṁ_out · h_out = Σ ṁ_in,i · h_in,i
+P_out = P_in,i   (ideal junction)
+```
+
+### Residuals & `n_equations()`
+
+Mixing mass + energy + pressure equality constraints as implemented.
+
+### Ports
+
+`inlet_0` … `inlet_{n-1}`, `outlet`.
+
+### Calibration
+
+None by default.
+
+### JSON
+
+| Key | Meaning | Default |
+|-----|---------|---------|
+| `n_inlets` | number of inlets | ≥ 2 |
+
+---
+
+## FR
+
+### But
+
+**Mélangeur** N → 1. Conservation ṁ et H ; pression commune idéale.
+
+### JSON
+
+Voir EN.