Summary

Support Qwen3-Omni thinker inference in the PyTorch backend.

This PR adds Qwen3-Omni model registration, HF processor integration, and multimodal preprocessing for image, video, audio, and mixed image/audio/video inputs. Audio support is currently limited to Qwen3-Omni.

Changes

• Add Qwen3-Omni PyTorch thinker model support.
• Add Qwen3-Omni VL preprocessor using the shared get_input_prompt -> preprocess path.
• Support image-only, video-only, audio-only, and mixed image/audio/video prompts.
• Keep Qwen3-Omni video expansion as whole-video spans, distinct from Qwen3VL per-frame timestamp handling.
• Add audio media parsing for OpenAI-style multimodal messages.
• Add multimodal input docs and examples, including Qwen3-Omni audio usage.

Notes

• Talker/audio-generation support is not included.
• Audio input support is scoped to Qwen3-Omni.
• Advanced use_audio_in_video=True interleaving is not enabled in this patch.

Related

Prerequisite PR

• Support video inputs #4360
• Mixed modality #4531