- Bundle Node.js inside the app (downloaded at build time)
- Add scripts/download-node.sh for macOS/Linux
- Add scripts/download-node.ps1 for Windows
- Fix PATH handling for cross-platform (: vs ;)
- Disable nvm/nvmrc to avoid conflicts with bundled Node
- npm global installs go to isolated app directory
- Update README with build instructions

Trainees just:
1. Download app
2. Add API key in Settings
3. Run: npm install -g @openai/codex
4. Run: codex "create something"