POST /jobs/thumbnails {mode: "convert"} starts "Convert outdated
thumbnails" under the thumbnail job's kind, guarded admission, worker
threads and cancel at a file boundary. For each file whose preview is
in another format, it writes the new preview from the source (atomic,
verified; a video with no decodable frame fails instead of getting the
placeholder), then removes that file's old-format previews in its
thumbnails folder. A failure keeps the old preview; orphan previews
and links are never touched. The final line reports converted, failed
and bytes before and after. The plan counts it with mode=convert; the
legacy gallery stream refuses to attach to a running conversion.
Vito Sansevero
80da6f125e