Card — header + body
Card is a surface container. CardHeader { title, subtitle } sits above
a CardBody separated by a 1px divider. Used everywhere the editor groups
related controls — recording metadata, timeline, export presets.
The composition pattern (<Card> <CardHeader/> <CardBody>…</CardBody> </Card>) is rust-ui-flavored: small composable building blocks rather than
a single fat component with a dozen props.