* cherry-pick 95191a3: AV1 raw format support and protocol mux/demux integration
* feat(rtp/av1): 完善 AV1 RTP 封装分片及关键帧检测
- Implements RTP packetization for AV1 with OBU fragmentation per RFC9304
- Adds accurate detection of AV1 keyframes using OBU inspection
- Updates AV1 RTP demuxing to reconstruct fragmented OBUs
- Ensures keyframe (IDR) flag is set correctly throughout mux/demux pipeline
---------
Co-authored-by: engine-labs-app[bot] <140088366+engine-labs-app[bot]@users.noreply.github.com>
- Refactor frame converter implementation
- Update mp4 track to use ICodex
- General refactoring and code improvements
🤖 Generated with [Claude Code](https://claude.ai/code)
Co-Authored-By: Claude <noreply@anthropic.com>