Add concise README to repository (#37)

* Add README.md with project overview and getting started guide

* Remove inaccurate offline support claim from README

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Co-authored-by: Claude <noreply@anthropic.com>

README.md

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+# Grimoire
+
+A Nostr protocol explorer and developer tool with a tiling window manager interface.
+
+## Features
+
+- **Tiling Windows** - Each window is a Nostr "app" (profile viewer, event feed, NIP docs, etc.)
+- **Command Palette** - Unix-style commands via `Cmd+K` to open apps and navigate
+- **Multi-workspace** - Virtual desktops with independent layouts
+- **Real-time** - Reactive event subscriptions with automatic updates
+
+## Stack
+
+React 19, TypeScript, Vite, TailwindCSS, Jotai, Dexie, Applesauce
+
+## Getting Started
+
+```bash
+npm install
+npm run dev
+```
+
+## Scripts
+
+| Command | Description |
+|---------|-------------|
+| `npm run dev` | Start dev server |
+| `npm run build` | Build for production |
+| `npm test` | Run tests in watch mode |
+| `npm run lint` | Lint code |
+| `npm run format` | Format code |
+
+## License
+
+MIT