Initial scaffold: pnpm workspace monorepo with backend + frontend

- Backend: Express + WebSocket proxy (tsx watch, strict TS, ESM)
- Frontend: React 19 + Vite + Monaco + Tailwind v4 + Tauri v2
- pnpm workspace at root for single-install workflow
- AGENTS.md with architectural constraints and commands
- Removed Tauri greet demo, added minimal App shell
- No external database, Git-as-Database philosophy

typst-leaf-backend/src/index.ts

@@ -0,0 +1,27 @@
+import { createServer } from "http";
+import { WebSocketServer } from "ws";
+
+const PORT = Number(process.env.PORT) || 4000;
+
+const server = createServer((_req, res) => {
+  res.writeHead(200, { "Content-Type": "application/json" });
+  res.end(JSON.stringify({ status: "ok", service: "typst-leaf-backend" }));
+});
+
+const wss = new WebSocketServer({ server });
+
+wss.on("connection", (ws) => {
+  console.log("WebSocket client connected");
+
+  ws.on("message", (data) => {
+    console.log("Received:", data.toString());
+  });
+
+  ws.on("close", () => {
+    console.log("WebSocket client disconnected");
+  });
+});
+
+server.listen(PORT, () => {
+  console.log(`Backend running on http://localhost:${PORT}`);
+});