App template on qcobjects 2.7.3.

- card.css selectors are scoped under both :root and :host, so the
  stylesheet applies whether a card renders at document level or inside a
  shadow root. The cards produced by $mapper inside github-grid are
  shadowed, while the same sheet is what a non-shadowed card loads at
  document level; bare selectors only matched in whichever context they
  happened to be loaded into.
- ::slotted() rules verified separately under :host.

No JS or TS change. Verified: computed styles identical in both contexts,
60 cards render with border-radius 30px and their box-shadow, 6 specs 0
failures, 145 components build.