Editor panel — card wrapping dope sheet
Composition: a Card with CardHeader ("Timeline · 4 tracks · 8.0s") and a
CardBody containing the DopeSheet. This is the expected production
placement in the editor — title and metadata up top, the timeline grid
underneath.
It's also the canary that catches "two correct components compose incorrectly" bugs: padding, scroll behavior, the playhead's vertical extent all have to coexist with the card's overflow and corner radius. The SSR snapshot test locks this composition's HTML alongside the isolated views.