`qbz-models` is the base of the dependency graph and cannot reach
`qbz-source`, so `artwork_ref_with_plex` knows exactly one remote word:
"plex". A `jellyfin:<albumId>/<tag>` token fell through to its LocalFile
arm, which handed MPRIS a file:// URI to a path that does not exist —
the bar and the queue were fine (they resolve through the Qt art cache),
only MPRIS was blank.
Resolve source-tagged tokens in the Qt layer, where `qbz-source` IS
reachable, and hand qbz-models an already-resolved local path.
Verified over the session bus: a Jellyfin track now reports
mpris:artUrl -> a real 256x256 JPEG in the image cache.
cc
vicrodh
df409f6c3c