chore: scaffold Tauri 2 + Svelte 5 workspace

Standard Tauri layout with a Svelte 5 + TypeScript + Vite frontend and a
Rust backend in src-tauri. Adds build tooling, app/window config,
capabilities, generated icons and the project README.

README.md

@@ -0,0 +1,127 @@
+# Mermix
+
+A cross-platform **Mermaid diagram editor & viewer** with **Git-backed projects**.
+Organize many diagrams into projects, edit them with a live preview, export to
+SVG/PNG, and version everything with real Git branches and commits — all in a
+native desktop app.
+
+Built with **Rust + Tauri 2**, **SQLite (sqlx)**, **git2**, and a **Svelte 5 +
+TypeScript** frontend using **CodeMirror 6** and **Mermaid 11**.
+
+---
+
+## Features
+
+- **Projects** — each project is a folder on disk that is a real Git repository
+  with a `mermix.toml` config and a `diagrams/` directory of `.mmd` files.
+- **Many diagrams per project** with a sidebar explorer; create, rename, delete.
+- **Live editor + preview** — CodeMirror source on the left, debounced Mermaid
+  render on the right, with zoom/pan and inline syntax-error reporting.
+- **Git version control built in** — view the working-tree status, write commit
+  messages, browse history, create branches and switch between them. Each branch
+  keeps its own set of diagrams, just like normal Git.
+- **Export** the current diagram to **SVG** or **PNG** (2× scale).
+- **Project registry** — recently opened projects are remembered in a local
+  SQLite database so you can jump back in from the start screen.
+- **Themes** — switch the Mermaid theme (default / neutral / dark / forest /
+  base) per project.
+
+## Architecture
+
+```
+Mermix/
+├─ src/                     # Svelte 5 + TS frontend
+│  ├─ App.svelte            # layout, resizable editor/preview split
+│  ├─ lib/
+│  │  ├─ api.ts             # typed wrappers over Tauri commands
+│  │  ├─ store.svelte.ts    # central rune-based app state
+│  │  ├─ mermaid.ts         # render + error capture
+│  │  ├─ export.ts          # SVG / PNG export via save dialog
+│  │  └─ components/        # Sidebar, Editor, Preview, GitPanel, Toolbar, …
+│  └─ main.ts
+└─ src-tauri/               # Rust backend
+   ├─ src/
+   │  ├─ lib.rs             # Tauri builder, state, command registry
+   │  ├─ commands.rs        # the IPC surface
+   │  ├─ db.rs              # sqlx/SQLite project registry + settings
+   │  ├─ project.rs         # mermix.toml, create/open, slugify
+   │  ├─ diagram.rs         # .mmd CRUD, frontmatter titles
+   │  ├─ git_ops.rs         # git2: commit, history, branches, status
+   │  ├─ error.rs / state.rs
+   │  └─ tests.rs           # headless core-logic tests
+   └─ tauri.conf.json
+```
+
+**Data model.** Mermix keeps one small app-level SQLite database (in the OS app
+data directory) that only tracks the *registry* of known projects and user
+settings. All real content lives on disk inside each project's Git repository —
+so projects are portable, inspectable, and work with any other Git tooling.
+
+A project on disk looks like:
+
+```
+my-diagrams/
+├─ mermix.toml          # project id, name, description, default theme
+├─ README.md
+├─ .gitignore
+├─ .git/                # full Git history
+└─ diagrams/
+   ├─ welcome.mmd
+   └─ login-flow.mmd    # Mermaid source, optional YAML frontmatter title
+```
+
+## Prerequisites
+
+- **Rust** (stable) and **Cargo**
+- **Node.js** 18+ and npm
+- Platform webview deps:
+  - **macOS** — nothing extra (system WebKit)
+  - **Windows** — WebView2 (preinstalled on Windows 11)
+  - **Linux** — `webkit2gtk` and related packages (see Tauri docs)
+
+## Getting started
+
+```bash
+npm install          # install frontend deps + Tauri CLI
+
+npm run app:dev      # run the desktop app in dev mode (hot reload)
+npm run app:build    # build a production bundle for your platform
+```
+
+Other useful scripts:
+
+```bash
+npm run dev          # frontend only (Vite) on http://localhost:1420
+npm run build        # type-check + build the frontend bundle
+npm run check        # svelte-check type checking
+```
+
+Backend logic is covered by headless tests:
+
+```bash
+cd src-tauri && cargo test
+```
+
+## Keyboard shortcuts
+
+| Shortcut            | Action                |
+| ------------------- | --------------------- |
+| `⌘/Ctrl + S`        | Save current diagram  |
+| `⌘/Ctrl + Enter`    | Commit (in commit box)|
+| `⌘/Ctrl + scroll`   | Zoom the preview      |
+
+## How Git is used
+
+- Creating a project runs `git init` (default branch `main`) and makes an
+  initial commit.
+- **Commit** stages every change (adds, edits, deletes) and records it with the
+  message you type; the author defaults to your global Git identity, falling back
+  to `Mermix <mermix@localhost>` if none is configured.
+- **Branches** are listed in the Git panel; create one and Mermix checks it out
+  for you. Switching branches reloads the diagram list from that branch.
+- **History** shows the most recent commits with short SHA, message, author and
+  relative time.
+
+## License
+
+MIT