Full-bleed lost the inset frame entirely — "¿dónde está el radio
interior?". A 16:10 cover can't be concentric on all 4 corners at full
(its height caps every corner to ~half-height), but its TOP corners CAN
match the card if the bottom stays square — the iOS-player geometry.
CSS can't read the card's dimension-capped radius (computed value is
still 9999px; the cap is a *used* value), so measure it via
ResizeObserver (min(w,h)/2 − gap) and apply to the cover's top corners;
bottom corners square, meeting the metadata. The inset frame is kept on
top/sides so the inner radius reads.
Finite radii unchanged (full 4-corner concentric). Toggle at full shows
"auto: solo top". Docs reconciled in SHAPE_ENGINE_RFC §5 + THEMING §30.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>