Implements all 13 actionable findings from the video feature review
(finding #11 skipped — would require core PixelFormat serde changes):

WebM muxer (webm.rs):
- Add shutdown/cancellation handling to the receive loop via
  tokio::select! on context.control_rx, matching the pattern used
  by the OGG muxer and colorbars node (fix #1, important)
- Remove dead chunk_size config field and DEFAULT_CHUNK_SIZE constant;
  update test that referenced it (fix #2, important)
- Make Seek on Live MuxBuffer return io::Error(Unsupported) instead of
  warn-and-clamp to fail fast on unexpected seek calls (fix #3, important)
- Add comment noting VP9 CodecPrivate constants must stay in sync with
  encoder config in video/mod.rs (fix #4, important)
- Make OpusHead pre_skip configurable via WebMMuxerConfig::opus_preskip_samples
  instead of always using the hardcoded constant (fix #6, minor)
- Group mux_frame loose parameters into MuxState struct (fix #12, nit)
- Fix BitReader::read() doc comment range 1..=16 → 1..=32 (fix #14, nit)

VP9 codec (vp9.rs):
- Add startup-time ABI assertion verifying vpx_codec_vp9_cx/dx return
  non-null VP9 interfaces (fix #5, minor)

Colorbars (colorbars.rs):
- Add draw_time_use_pts config option to stamp PTS instead of wall-clock
  time, more useful for A/V timing debugging (fix #7, minor)
- Document studio-range assumption in SMPTE bar YUV table comment with
  note explaining why white Y=180 (fix #13, nit)

OGG muxer (ogg.rs):
- Remove dead is_first_packet field and its no-op toggle (fix #10, minor)

Tests (tests.rs):
- Add File mode (WebMStreamingMode::File) test exercising the seekable
  temp-file code path (fix #8, minor)
- Add edge-case tests: non-keyframe first video packet and truncated/
  corrupt VP9 header — verify no panics (fix #9, minor)

Signed-off-by: StreamKit Devin <devin@streamkit.dev>
Signed-off-by: bot_apk <apk@cognition.ai>
Co-Authored-By: Staging-Devin AI <166158716+staging-devin-ai-integration[bot]@users.noreply.github.com>

Implements all 13 actionable findings from the video feature review
(finding #11 skipped — would require core PixelFormat serde changes):

WebM muxer (webm.rs):
- Add shutdown/cancellation handling to the receive loop via
  tokio::select! on context.control_rx, matching the pattern used
  by the OGG muxer and colorbars node (fix #1, important)
- Remove dead chunk_size config field and DEFAULT_CHUNK_SIZE constant;
  update test that referenced it (fix #2, important)
- Make Seek on Live MuxBuffer return io::Error(Unsupported) instead of
  warn-and-clamp to fail fast on unexpected seek calls (fix #3, important)
- Add comment noting VP9 CodecPrivate constants must stay in sync with
  encoder config in video/mod.rs (fix #4, important)
- Make OpusHead pre_skip configurable via WebMMuxerConfig::opus_preskip_samples
  instead of always using the hardcoded constant (fix #6, minor)
- Group mux_frame loose parameters into MuxState struct (fix #12, nit)
- Fix BitReader::read() doc comment range 1..=16 → 1..=32 (fix #14, nit)

VP9 codec (vp9.rs):
- Add startup-time ABI assertion verifying vpx_codec_vp9_cx/dx return
  non-null VP9 interfaces (fix #5, minor)

Colorbars (colorbars.rs):
- Add draw_time_use_pts config option to stamp PTS instead of wall-clock
  time, more useful for A/V timing debugging (fix #7, minor)
- Document studio-range assumption in SMPTE bar YUV table comment with
  note explaining why white Y=180 (fix #13, nit)

OGG muxer (ogg.rs):
- Remove dead is_first_packet field and its no-op toggle (fix #10, minor)

Tests (tests.rs):
- Add File mode (WebMStreamingMode::File) test exercising the seekable
  temp-file code path (fix #8, minor)
- Add edge-case tests: non-keyframe first video packet and truncated/
  corrupt VP9 header — verify no panics (fix #9, minor)

Signed-off-by: StreamKit Devin <devin@streamkit.dev>
Signed-off-by: bot_apk <apk@cognition.ai>
Co-authored-by: bot_apk <apk@cognition.ai>
Co-authored-by: Staging-Devin AI <166158716+staging-devin-ai-integration[bot]@users.noreply.github.com>