Collections opened as a bare poster grid under a plain app bar: no
collection artwork, no summary, no count, so they looked unrelated to
the movie/show and album pages around them (#1493).
The collection screen now leads with the same header the album and
artist pages use: the collection poster (square for music collections)
beside its title, item count, year span, content rating and collapsible
summary, with the Play / Shuffle / Download / Delete row underneath.
The collection's backdrop art washes the header region behind a scrim
that fades to the scaffold background before the grid starts; a
collection with only a poster gets a blurred copy of it instead so the
wash still reads as colour. A transparent title bar fades in once the
header scrolls away, and the circular back button matches the detail
pages. The year span is only shown once every page has loaded so a
partially fetched collection never reports a narrower range.
buildDetailScaffold gains optional `behind`/`above` layers so a detail
screen can paint art under, and chrome over, its scroll view without
re-implementing the overlay-sheet host and back handling.
Verified on Pixel 9a, 10" tablet and Android TV emulators: touch scroll
and pinned title, D-pad up from the grid lands on the action row and
scrolls the header back into view, D-pad back pops, Plex collection with
art and Jellyfin collection without art.
edde746
a873009fff