feat(cli): add initial CLI implementation with argument parsing and prompt handling

- Created package.json and package-lock.json for CLI package.
- Implemented argument parsing in args.ts to handle various flags and commands.
- Developed main CLI logic in cli.ts to execute commands and handle errors.
- Added configuration loading from a JSON file in config.ts, with environment variable support.
- Implemented prompt resolution and provider interaction in prompt.ts.
- Added usage documentation for the CLI.
- Configured TypeScript settings in tsconfig.json for the CLI package.
- Updated README in vscode package to reflect the new CLI functionality.
- Refactored root tsconfig.json to streamline project structure.

CONTRIBUTING.md

@@ -0,0 +1,62 @@
+# Contributing to LexAI
+
+Thanks for helping improve LexAI. This project is a monorepo with three user-facing packages plus a shared library.
+
+## Code of Conduct
+
+Please read and follow the [Code of Conduct](CODE_OF_CONDUCT.md).
+
+## Ways to contribute
+
+- Bug reports and reproducible issues
+- Documentation fixes
+- Small, focused pull requests (one concern per PR)
+- Discussions on design when a change is large or security-sensitive
+
+## Development setup
+
+**Requirements:** Node.js **22+**, npm 11+ (see `packageManager` in root `package.json`).
+
+```bash
+git clone https://git.juankibin.space/kibin/LexAI.git
+cd LexAI
+npm run install:all
+```
+
+### Useful scripts (from repo root)
+
+| Script | Purpose |
+| --- | --- |
+| `npm run chrome:dev` | Chrome extension with hot reload |
+| `npm run chrome:build` | Production Chrome build |
+| `npm run chrome:typecheck` / `chrome:test` | Typecheck & unit tests |
+| `npm run vscode:build` / `vscode:typecheck` | VS Code extension |
+| `npm run cli:build` / `cli:typecheck` | CLI Prompt Builder |
+| `npm run typecheck:all` / `build:all` | All packages |
+
+Shared code lives in `src/lib/`. **Do not** import `@lib/crypto` or `@lib/messaging` from `packages/vscode` or `packages/cli` (Chrome-only).
+
+### Package-specific notes
+
+- **Chrome:** load unpacked from `packages/chrome/.output/chrome-mv3` after build. Selection/replace is DOM-timing-sensitive — verify on a real page for UI changes.
+- **VS Code:** build then F5 or Install from VSIX (`packages/vscode`).
+- **CLI:** set `LEXAI_API_KEY`; never commit keys or put them in `~/.lexai/config.json`.
+
+## Pull request process
+
+1. Fork / branch from `main` (or `develop` if that is the active integration branch).
+2. Keep changes scoped; update docs when behavior changes.
+3. Run the checks that touch your change, at minimum:
+   - Shared lib / Chrome: `npm run chrome:typecheck` and `npm run chrome:test`
+   - VS Code: `npm run vscode:typecheck` and `npm run vscode:build`
+   - CLI: `npm run cli:typecheck` and `npm run cli:build`
+4. Open a PR using the [pull request template](.gitea/PULL_REQUEST_TEMPLATE.md).
+5. Do not include secrets, API keys, or personal data in commits or screenshots.
+
+## Security
+
+If you discover a vulnerability (especially around API key handling or data exfiltration), **do not** open a public issue with exploit details. Contact the maintainer privately (see the Chrome Web Store listing / repository owner).
+
+## License
+
+By contributing, you agree that your contributions will be licensed under the [MIT License](LICENSE).