Run VibeVoice and KugelAudio natively on Transformers 5
Technical details:
- Add compatibility shims for Transformers 5 tokenizer, registration, generation, cache, dtype, and weight-tying APIs
- Materialize VibeVoice and KugelAudio diffusion scheduler state on CPU during meta-device model construction
- Remove the VibeVoice runtime selector and force legacy workflow values onto the main environment
- Update engine metadata and documentation to reflect native Transformers 5 support
- Suppress expected VibeVoice tied-weight and compatibility warnings