- Removed unified_ffmpeg_player.go and unified_player_adapter.go
- Updated frame_player_gstreamer.go to remove UnifiedPlayer fallback
- Updated frame_player_default.go to return error when GStreamer unavailable
- Updated PROJECT_STATUS.md: Player module now fully implemented with GStreamer
- Removed critical issues note about Player A/V sync problems
GStreamer is now the sole playback backend, providing stable A/V
synchronization and frame-accurate seeking. The broken FFmpeg pipe-based
UnifiedPlayer has been completely removed.