Artists tab 404: client called /api/library/artists, but the server
mounts the artists list at /api/artists (handleListArtists). Albums
sit at /api/library/albums for historical reasons — the paths aren't
symmetric. Switch listArtists() to /api/artists with sort=alpha.
Albums tab grid: matched the responsive 3-up layout we built for
artist detail. LayoutBuilder computes cellW from available width;
AlbumCard sized to the cell with titleMaxLines: 2; mainAxisExtent
matches actual content height (cover + 2-line title + artist line +
fudge). No more wide-aspect cells with empty space below the card.
Also wired `extra: ref` on the artists/albums grids and the Liked
tab so detail-screen nav hydration kicks in here too — taps from
library screens get the same instant header that home tiles do.