Closes the slice-4 'plex rows render basic' deferral: local-playlist plex
refs bulk-resolve from the plex cache by rating key (new qbz-plex
by-keys getter with the cached-track shape) into full-metadata rows -
real titles, duration, PlexThumb artwork, playable through the existing
plex path (induced offline allowed). Cache misses render an honest
'Unavailable Plex track' fallback and legacy garbage refs (plex synthetic
ids stored as qobuz ids by the pre-typed-drag flow) surface as removable
unavailable rows instead of being D11-hidden forever.
Still-live writers of that garbage are fixed: the shared add-to-playlist
arm routes plex:<key>/local refs through the local picker and refuses
synthetic ids with a toast; row_drag_track no longer falls through plex
rows to the Qobuz arm; and add_qobuz/add_drag blocking writers refuse ids
at or above the plex synthetic floor as a last gate. main.rs also carries
the context-menu mixtape/favorite arms from the previous commit.
cc
vicrodh
47c315251c