Four-part change to push more surfaces onto the drift cache and
eliminate cold-tab-visit latency on the Library screen.
* **Library Artists tab** — _libraryArtistsProvider migrates from
REST-paginated AsyncNotifier with infinite-scroll loadMore to a
drift-first StreamProvider over cached_artists ordered by
sortName. Sync already populates the full set; cacheFirst's
fetchAndPopulate covers the fresh-install + sync-not-yet-done
cold case via /api/artists?limit=1000. SWR refresh on every
visit. GridView.builder lazily realizes only visible cells so
loading the full list up front is fine for typical libraries.
loadMore + NotificationListener gone.
* **Library Albums tab** — same migration, drift-first over
cached_albums joined with cached_artists for the artistName
field.
* **systemPlaylistsStatusProvider** — new CachedSystemPlaylistsStatus
single-row table (schema 6 → 7, JSON blob like CachedHomeSnapshot)
for the home Playlists row's "building / pending / failed"
placeholder logic. Drift-first means the row paints with the
prior status instantly instead of flickering through
SystemPlaylistsStatus.empty() while the REST call resolves.
* **Library screen tab pre-warm** — ref.listen on all 5 tab
providers in _LibraryScreenState.build subscribes them upfront
so swiping between tabs feels instant rather than each tab
paying its own cold-cache cost on first visit. cacheFirst
handles dedupe of concurrent fetchAndPopulate triggers.
Test mock updated for the StreamProvider type change on
systemPlaylistsStatusProvider.