Add web/ — PTY+WebSocket server, xterm.js PWA client, Dockerfile, and PyInstaller notes

web/README.md

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+# web/ — Kanjin Web Server & PWA
+
+## Quick start (Docker)
+
+From the project root:
+
+```bash
+docker build -t kanjin -f web/Dockerfile .
+docker run -p 8080:8080 kanjin
+```
+
+Open http://localhost:8080 in any browser. On Chrome/Edge you can **"Install as app"** via the address bar icon — removes the URL bar and adds a home-screen icon.
+
+## Windows standalone .exe
+
+From the project root, with PyInstaller installed:
+
+```bash
+pip install pyinstaller
+pyinstaller --onefile --name Kanjin main.py
+```
+
+Deliver `dist/Kanjin.exe` — no Python or dependencies needed on the player's machine.
+
+## Development
+
+```bash
+cd web
+python -m pip install -r requirements.txt
+python generate_icons.py
+python server.py    # starts uvicorn on :8080 with hot-reload
+```
+
+Requires Linux or WSL (uses `pty`). The server spawns `main.py` from the parent directory in a pseudo-terminal and streams it to the browser over WebSocket.
+
+## File layout
+
+| Path | Purpose |
+|---|---|
+| `server.py` | FastAPI app: serves index.html, mounts /static, handles /ws WebSocket |
+| `static/index.html` | xterm.js in-browser terminal connected over WebSocket |
+| `static/manifest.json` | PWA manifest — enables Chrome "Install as app" |
+| `static/sw.js` | Service worker — precaches the shell for offline launch |
+| `static/generate_icons.py` | Generates placeholder PNG icons (run once) |
+| `requirements.txt` | Python deps (fastapi, uvicorn) |
+| `Dockerfile` | Multi-stage Docker build |