docs: add CONTRIBUTING.md with dev setup and PR guidelines

CONTRIBUTING.md

@@ -0,0 +1,79 @@
+# Contributing to ClawChat
+
+Thanks for your interest in contributing! 🦞
+
+## Getting Started
+
+1. **Fork** the repository
+2. **Clone** your fork:
+   ```bash
+   git clone https://github.com/<your-username>/clawchat.git
+   cd clawchat
+   ```
+3. **Install dependencies:**
+   ```bash
+   npm install
+   ```
+4. **Set up your environment:**
+   ```bash
+   cp .env.example .env
+   # Edit .env with your OpenClaw gateway details
+   ```
+5. **Start the dev server:**
+   ```bash
+   npm run dev
+   ```
+
+## Development
+
+- **Build:** `npm run build` — must pass with 0 errors before submitting a PR
+- **Dev server:** `npm run dev` — starts Vite with hot reload
+- **Preview:** `npx vite preview` — serve the production build locally
+
+### Project Structure
+
+```
+src/
+├── components/     # React components
+│   ├── chat/       # Chat area (messages, input, streaming)
+│   └── sidebar/    # Session list sidebar
+├── hooks/          # Custom React hooks (WebSocket, sessions)
+├── lib/            # Utilities (markdown, formatting)
+├── types/          # TypeScript type definitions
+├── App.tsx         # Root component
+└── main.tsx        # Entry point
+```
+
+## Making Changes
+
+1. Create a feature branch: `git checkout -b feat/my-feature`
+2. Make your changes
+3. Ensure `npm run build` passes with no errors
+4. Commit using [Conventional Commits](https://www.conventionalcommits.org/):
+   - `feat:` — new feature
+   - `fix:` — bug fix
+   - `docs:` — documentation only
+   - `refactor:` — code change that neither fixes a bug nor adds a feature
+   - `style:` — formatting, missing semicolons, etc.
+   - `perf:` — performance improvement
+   - `ci:` — CI/CD changes
+5. Push and open a Pull Request
+
+## Reporting Issues
+
+When filing an issue, please include:
+- Browser and version
+- Steps to reproduce
+- Expected vs actual behavior
+- Console errors (if any)
+
+## Code Style
+
+- TypeScript strict mode
+- Tailwind CSS v4 for styling (no inline styles)
+- Functional React components with hooks
+- Keep components focused and small
+
+## License
+
+By contributing, you agree that your contributions will be licensed under the [MIT License](LICENSE).

README.md

@@ -77,6 +77,10 @@ Or serve the `dist/` folder with nginx, Caddy, or any static file server.
 
 [MIT](LICENSE) © Nicolas Varrot
 
+## 🤝 Contributing
+
+Contributions are welcome! See [CONTRIBUTING.md](CONTRIBUTING.md) for guidelines.
+
 ## 🔗 Links
 
 - [OpenClaw](https://github.com/openclaw/openclaw) — the AI agent platform ClawChat connects to