fix: implement review findings for VP9, colorbars & WebM

[staging-devin-ai-integration]

fix: implement review findings for VP9, colorbars & WebM

Summary

Implements 13 of 14 actionable findings from the code review of the video feature branch (VP9 Codec, Colorbars & WebM Container area). Finding #11 (pixel_format String→enum) was skipped as it would require modifying the core PixelFormat serde representation, risking API breakage.

Changes by file

WebM muxer (webm.rs):

• Fix fix(tools): install script #1 (important): 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 docs: improve UI documentation #2 (important): Remove dead chunk_size config field and DEFAULT_CHUNK_SIZE constant
• Fix fix(plugins): resolve flaky native plugin reload test #3 (important): Make Seek on Live MuxBuffer return io::Error(Unsupported) instead of warn-and-clamp
• Fix docs: remove redundant note #4 (important): Add comment noting VP9 CodecPrivate constants must stay in sync with encoder config
• Fix fix(docs): http API inaccuracy #6 (minor): Make OpusHead pre_skip configurable via WebMMuxerConfig::opus_preskip_samples
• Fix docs: add clarity on use of custom packet type #12 (nit): Group mux_frame loose parameters into MuxState struct
• Fix fix(monitor): throttle stats, show slow mixer edges, and improve moq_peer counters #14 (nit): Fix BitReader::read() doc comment range 1..=16 → 1..=32

VP9 codec (vp9.rs):

• Fix Built-in authentication #5 (minor): Add startup-time ABI assertion verifying vpx_codec_vp9_cx/dx return non-null VP9 interfaces

Colorbars (colorbars.rs):

• Fix chore: proper notice file #7 (minor): Add draw_time_use_pts config option to stamp PTS instead of wall-clock time
• Fix feat(ui): dynamically adapt MoQ URL based on selected pipeline #13 (nit): Document studio-range assumption in SMPTE bar YUV table comment

OGG muxer (ogg.rs):

• Fix Playwright E2E tests #10 (minor): Remove dead is_first_packet field and its no-op toggle

Tests (tests.rs):

• Fix docs: add Grafana dashboard screenshot #8 (minor): Add File mode (WebMStreamingMode::File) test
• Fix fix(ui/design): load dynamic samples, preserve edges, order YAML by canvas #9 (minor): Add edge-case tests: non-keyframe first video packet, truncated VP9 header

Review & Testing Checklist for Human

• Shutdown behavior: Verify that the WebM muxer stops promptly when a Shutdown control message is sent while both audio and video streams are active. The tokio::select! uses biased; with shutdown checked first.
• Seek error in Live mode: The MuxBuffer::Live Seek impl now returns Err(Unsupported). Verify that Live mode still works correctly end-to-end (the Writer::new_non_seek path should never call seek, but confirm no regression).
• OpusHead pre_skip: The opus_head_codec_private function now accepts a pre_skip parameter. Default is still 312. Verify audio playback is correct with a real Opus stream.
• File mode test: Run cargo test -p streamkit-nodes test_webm_mux_file_mode and verify it passes (exercises the temp-file seekable path).
• Edge-case tests: Run cargo test -p streamkit-nodes test_webm_mux_non_keyframe_first_video test_webm_mux_truncated_vp9_header — these verify no panics on bad input.

Notes

• just lint and just test both pass (0 failures).
• Finding feat: implement Playwright e2e tests infra #11 (use typed PixelFormat enum for colorbars config) was deliberately skipped: PixelFormat in crates/core/src/types.rs has Serialize/Deserialize but no #[serde(rename_all = "lowercase")], so changing the config type would break existing pipelines that use "nv12" etc.
• Requested by Claudio.

Devin Session: https://staging.itsdev.in/sessions/c2bb8883fc514013b37fd9ace9195d04

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[staging-devin-ai-integration]

✅ Devin Review: No Issues Found

Devin Review analyzed this PR and found no potential bugs to report.

View in Devin Review to see 5 additional findings.

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