feat(browser-actions): add high-fidelity video capture

[chubes4]

Summary

Adds opt-in high-quality video capture for wordpress.browser-actions. Instead of Playwright's realtime recorder, it captures device-scale PNG frames and encodes a VP9/WebM video once at the end, preserving the existing marker timeline and reporting dimensions and fps.

What changed

• Added the validated video-quality=default|high argument; the default recording path remains unchanged.
• High mode captures viewport screenshots at device scale on a 10 fps schedule and encodes them with ffmpeg using VP9 at CRF 18.
• High-mode video metadata reports viewport × deviceScaleFactor dimensions and 10 fps; marker data continues to use the recording's monotonic timeline.
• Added browser regression coverage decoding a 540×960 viewport at DPR 2 and verifying 1080×1920 output, fps, and marker metadata.

How to test

1. Run npm ci && npm run build && npm run test:browser-video-capture; expect passes as recorded by Cook's deterministic gate.

Compatibility

Opt-in and backward-compatible: existing captures retain the Playwright recorder behavior. High mode requires ffmpeg available on PATH, via FFMPEG_PATH, or in the Playwright browser cache. It produces VP9 WebM and captures at 10 fps.

Evidence

• Verified command npm ci && npm run build && npm run test:browser-video-capture: status=succeeded; candidate commit 70085e33ad7c3d1e4c7e93ccdec526644421115d, tree 7c5b520ea581dbb4c1ba9ec9a6572e75befb360b, fingerprint 6dddb0c9d676d3e15a85054dd1a1ff80592f6e20c761726ef7978d6a326dfc07; durable gate gate-1
• Base unchanged since verification: main remains at 0faffbf.
• CI expected: Homeboy CI after push
• Candidate adoption provenance: the candidate was promoted from the recorded Cook task execution.
• Cook deterministic verification: 1 gate(s) completed green.
• Durable run execution: Succeeded
• Reviewer-resolvable evidence from source_refs[0]: browser-actions: crisp high-DPI video capture (record at device pixels, not 1 Mbps CSS-pixel VP8) #2559
• Task objective: Goal: an opt-in high-fidelity video capture mode for wordpress.browser-actions that records at device pixels (viewport x deviceScaleFactor) and encodes once at the end at high quality, with no realtime-encoder warm-up, keeping the markers timeline aligned. Start in packages/runtime-playground/src/browser-actions-runner.ts (recordVideo setup ~L224, video adoption ~L564, arg parsing ~L863-903), packages/runtime-core/src/command-registry.ts for the new arg, and tests/browser-actions-video-capture.browser.test.ts. Plain Playwright 1.61.1 recordVideo cannot do this (Chromium screencast is CSS-pixel), so use CDP Page.startScreencast with maxWidth/maxHeight at device pixels or timed screenshots, then ffmpeg (Playwright ships one under ms-playwright/ffmpeg-*; fall back to PATH).
• Verified candidate scope: 3 changed file(s): packages/runtime-core/src/command-registry.ts, packages/runtime-playground/src/browser-actions-runner.ts, tests/browser-actions-video-capture.browser.test.ts.
• Verified finalization base: main at 0faffbf
• deterministic gate passed: sh -lc npm ci && npm run build && npm run test:browser-video-capture (Passed)

AI assistance

• AI assistance: Yes
• Tool(s): Homeboy (opencode)
• Model: openai/gpt-6-luna
• Used for: [operator-only reference omitted]

[chubes4]

Finalized by Extra Chill Bot: CI's browser job failed with spawn ffmpeg ENOENT because the high-quality encoder only tried system ffmpeg. Now it resolves FFMPEG_PATH → Playwright's bundled ffmpeg (ms-playwright/ffmpeg-*) → PATH. Frames are piped as JPEG over pipe:0 and encoded as VP8 at high quality, which the minimal bundled build supports (it has no VP9/H.264, PNG decoder, or - protocol alias). The test decodes with the same resolved ffmpeg and asserts a 1080x1920 VP8 stream. All 5 video tests pass locally with and without a system ffmpeg on PATH; npm run build is clean.