Final review fixes for automatic previews:
- A video preview that cannot be made is the placeholder frame (no-store),
never the video; OpenCV failures fall through to ffmpeg and the
placeholder. Cards and the inspector cover swap back to the video
element when the preview image fails.
- View requests are admitted on the event loop (3 writers, one flight per
file, at most 64 waiting; past that the fallback at once). Writes run on
a small dedicated pool, never the default executor. The history route
shares the admission, flight key and link checks.
- Drive, UNC, empty and dot segments are refused as text; the folder
listing runs inside the admission.
- Holds are checked after the slot and again before the rename; only
decode failures are remembered.
- Bounded, logged shutdown: ffmpeg is killed, no worker restarts after
cleanup, and a reload stops the old worker.
- The listing says whether the preview file exists (thumbnail_ready) for
the legacy gallery's dot; media in a nested thumbnails folder keeps its
original; file names the server quotes match in the inspector.
Vito Sansevero
297b2060ee