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-frontend/.gitignore

@@ -0,0 +1,24 @@
+# Logs
+logs
+*.log
+npm-debug.log*
+yarn-debug.log*
+yarn-error.log*
+pnpm-debug.log*
+lerna-debug.log*
+
+node_modules
+dist
+dist-ssr
+*.local
+
+# Editor directories and files
+.vscode/*
+!.vscode/extensions.json
+.idea
+.DS_Store
+*.suo
+*.ntvs*
+*.njsproj
+*.sln
+*.sw?