Two RED tests pin D-20 (codec strict-mode, no silent fallback):
- 'throws on unsupported vp9 and emits RECORDING_ERROR'
- 'does not throw when vp9 IS supported'
vi.resetModules() between tests is critical: module-load side-effects
(handshake + port connect) happen once per import, so isolation across
the four test files depends on it.
chrome.runtime is stubbed locally (no vitest-chrome dependency added,
per threat T-1-NEW-02-01 — minimize supply chain for four test files).
No 'as any' / no '@ts-ignore'; the cast is 'as unknown as T'.
Plan 03 must export assertCodecSupported() from src/offscreen/recorder.ts.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
