The Home Playlists row now always renders the For You + Discover +
3× Songs-like slots: a real PlaylistCard when the system playlist
has generated, otherwise a PlaylistPlaceholderCard showing its
build state — building / failed / seed-needed / pending — derived
from GET /api/me/system-playlists-status. Mirrors Flutter's
_buildPlaylistsRow + PlaylistPlaceholderCard.
* SystemPlaylistsStatus domain + wire; MeApi.getSystemPlaylistsStatus;
HomeRepository.getSystemPlaylistsStatus.
* HomeViewModel fetches the status in refresh() and exposes it as a
StateFlow; HomeScreen collects it and threads it to the row builder.
* PlaylistPlaceholderCard widget (sized to match PlaylistCard) with
a status chip + variant subtitle.
* buildPlaylistsRow / variantFor port the slot logic; user playlists
follow the fixed system slots.
The offline-pool cards (§4.3) are NOT in this commit — Android has
no local recently-played cache (history is fetch-on-visit), so the
"Recently played" pool has no offline source. Deferring that half
until the history snapshot cache lands; see #28 notes.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
bvandeusen
edbc805333