- Add GitHub Actions workflow for cross-platform testing
- Test matrix: Ubuntu/macOS/Windows × Python 3.10/3.11/3.12
- Run full test suite on all platforms
- Verify basic functionality (GPU detection, memory info)
- Update README badge to show CI status
Improves platform compatibility confidence and catches platform-specific issues early.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
