Discover sections now use a Carousel: a clipped, sliding track of
album cards with prev/next page controls, paginated by slice like the
Svelte DiscoverySection. With no ScrollView the row height is exactly
the card height — the horizontal scrollbar no longer injects vertical
space, so the earlier internal-scroll problem is resolved structurally
rather than patched.
per-page is derived from the viewport width and self-corrects on
resize. Replaces SectionRow.
cc