feat: add CosyVoice 3 TTS backend, engine platform matrix, CONTRIBUTING.md (#39)
* feat: add CosyVoice 3 TTS backend, engine platform matrix, CONTRIBUTING.md
- Add CosyVoiceBackend adapter to tts_backend.py (9 langs + 18 dialects,
zero-shot voice cloning, instruct mode, Apache-2.0)
- Fix VoxCPM2Backend.is_available() — remove incorrect hard CUDA gate;
VoxCPM2 supports MPS (Apple Silicon) and CPU fallback
- Add unified TTS Engines table to README with features + platform compat
- Update FAQ to reflect current 6-engine Plugin SDK (was 'not yet')
- Add CONTRIBUTING.md with dev setup, PR workflow, TTS plugin guide,
code style conventions, and testing commands
- Move Contributing section above FAQ in README
* fix(pr): address CodeRabbit review feedback
- README: Update 'Plugin SDK' to 'built-in backend registry' for clarity
- tts_backend.py: Preserve full language codes for CosyVoice cross-lingual lookup before fallback
Palash Debnath
a6aa9d79e6