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/README.md

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+# Entropyk Web UI
+
+Visual canvas builder for Entropyk thermodynamic cycles.
+
+The UI emits the same `ScenarioConfig` JSON as the CLI
+(`crates/cli/src/config.rs`). Physics always runs through
+`entropyk_cli::run::simulate_from_json` via the Axum `ui-server`.
+
+## Prerequisites
+
+- Node.js 18+ and npm
+- The Rust API server running (see below)
+
+## Setup
+
+### 1. Start the Rust API server
+
+From the project root:
+
+```bash
+cargo run -p entropyk-demo --bin ui-server
+# → http://localhost:3030
+```
+
+Endpoints:
+- `GET  /api/health`
+- `GET  /api/components`
+- `POST /api/simulate`
+- `GET  /api/mollier?fluid=R134a`
+
+### 2. Start the Next.js dev server
+
+```bash
+cd apps/web
+npm install
+npm run dev
+# → http://localhost:3000
+```
+
+By default the frontend proxies `/api/entropyk/*` to `http://localhost:3030/api/*`
+(see `next.config.mjs`). To point at a different API, set:
+
+```bash
+ENTROPYK_API_URL=http://my-host:3030 npm run dev
+```
+
+## Usage
+
+1. Drag components from the left palette onto the canvas.
+2. Connect ports by dragging from one handle to another.
+3. Select a node to edit its parameters in the right panel.
+4. Pick the fluid and backend in the top bar.
+5. Click **Solve cycle** — the result panel shows COP, edge states and a P-h diagram.
+6. **Load** drops in a CLI example from the picker; **Import JSON** loads any CLI config.
+7. **Multi-run** sweeps parameters (fluid, UA, …) and solves cases in parallel.
+
+## Architecture
+
+```
+Browser (Next.js)         Rust API (Axum ui-server :3030)
+  React Flow canvas   →   POST /api/simulate
+  Zustand store             → simulate_from_json() (CLI engine)
+  Recharts P-h diagram  ←   SimulationResult JSON
+```
+
+Anything buildable in the UI can also be run with:
+
+```bash
+cargo run -p entropyk-cli -- run path/to/config.json
+```
+
+## Deprecated surfaces
+
+- `ui/` at the repo root — legacy static HTML; calls removed `/api/calculate`. Do not use.
+- `tools/circuit-builder-ui` — alternate HTML builder; prefer `apps/web`.