Fix compilation errors in SubcodecAnimationCacheImpl and
SubcodecMultiAnimationRendererImpl: NSData->Data sink closure types,
withSink->sink argument labels for advanceFrame/emitFrameIfNeeded,
unused variable warning, and redundant Void return assignment.
Add both modules as deps to ChatEntityKeyboardInputNode to verify
they compile in the full build.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
Implements utility helpers, BT.709 ARGB→YUV 4:2:0 conversion with alpha
un-premultiplication, and AnimationCacheItemWriterImpl that feeds frames
to SCSprite and writes metadata alongside the .mbs output.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>