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

VISION.md

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+# VISION: typst-leaf
+
+## 1. Product Philosophy
+**typst-leaf** is a high-performance, self-hosted LaTeX alternative built for the modern era. It rejects the bloated, slow architecture of traditional LaTeX editors in favor of the **Typst** ecosystem.
+
+It is designed for:
+1.  **Speed:** Sub-50ms compile times.
+2.  **Sovereignty:** Your data lives in a standard Git repository on your filesystem, not a proprietary database.
+3.  **Developer Experience:** First-class Vim support, fast LSP feedback, and CLI-based workflows.
+
+## 2. Architecture Overview
+The system follows a strict **Client-Server** model, even when running locally.
+
+### The Stack
+* **Monorepo Structure:** Flat directory structure (`typst-leaf-backend`, `typst-leaf-frontend`).
+* **Frontend:** React (Vite) + Monaco Editor.
+* **Desktop Wrapper:** Tauri v2 (integrated into `typst-leaf-frontend`).
+* **Backend:** TypeScript (Node.js/Bun) + Express/Fastify.
+* **Core Engine:** `tinymist` (Binary) for LSP and compilation.
+
+### Component Breakdown
+
+#### A. Backend (`typst-leaf-backend`)
+The backend is a stateless orchestration layer that sits on top of the file system.
+* **Role:**
+    * Spawns and manages the `tinymist` process.
+    * Proxies WebSocket connections for LSP (Language Server Protocol).
+    * Proxies WebSocket connections for the Preview (SVG stream).
+    * Exposes a REST API for file management (CRUD) and Git operations (`git commit`, `git push`).
+* **Data Source:** Standard OS file system. Each "Project" is a directory.
+
+#### B. Frontend (`typst-leaf-frontend`)
+A Single Page Application (SPA) that acts as the IDE interface.
+* **Editor:** Monaco Editor configured with `monaco-languageclient` to talk to the backend LSP.
+* **Preview:** A high-performance SVG renderer that receives delta updates from Tinymist.
+* **Vim Mode:** `monaco-vim` enabled by default or toggleable.
+* **Tauri Integration:** The frontend folder contains `src-tauri`, allowing it to build as a native desktop application.
+
+## 3. Critical Technical Decisions
+
+### 3.1 The "No-Database" Database
+We do not use MongoDB, Postgres, or SQL.
+* **State:** The state is the file system.
+* **History:** The history is the `.git` folder.
+* **Collaboration:** We do not implement Operational Transforms (OT) or CRDTs for simultaneous editing. Collaboration is handled via Git (Commit/Push/Pull) logic exposed in the UI.
+
+### 3.2 The Rendering Pipeline
+We **do not** render PDFs in the browser for preview.
+1.  User types in Monaco.
+2.  Frontend sends `textDocument/didChange` (LSP) to Backend.
+3.  Backend pipes to `tinymist`.
+4.  `tinymist` computes layout and pushes an **SVG** diff to the preview socket.
+5.  Frontend renders the SVG.
+*Rationale:* SVGs are selectable, zoomable without blur, and significantly lighter than streaming PDF binaries.
+
+### 3.3 The LSP Connection
+We use `monaco-languageclient` to connect Monaco to the backend via WebSocket. The backend simply pipes this socket to the stdin/stdout of the running `tinymist` binary. We do not reimplement LSP logic in TypeScript.
+
+## 4. User Stories
+* **As a User,** I want to type code and see the result instantly (<100ms lag).
+* **As a User,** I want to double-click an element in the preview and have my cursor jump to the code (SyncTeX/Source Mapping).
+* **As a User,** I want to hit `Cmd+S` to save to disk and `Cmd+Shift+S` to create a Git commit.