- html-schema: the previous clause claimed a composition host's data-media-start is
never read. It is: readElementPlaybackStart (media.ts:16) resolves
data-playback-start ?? data-media-start and timeline.ts calls it on composition
clips. Rewrote to the accurate reason both reviewers gave — composition hosts are
only inspected by the playback-start-first readers, media-start works as a
fallback, but playback-start is what Studio writes/normalises to.
- motion test: pin the HoverVideo click-suppression (preventDefault +
stopPropagation). Removing it left the gate 12/12; now it fails. This is the bug
that escaped static review and only surfaced by driving the live preview.
- replica-compare: fold the visible 'Sound off/on' text into the aria-label so the
accessible name contains it (WCAG 2.5.3, Rames).
Round-5 findings from Magi and Rames.