Tim (Discord): cover-art automation fails with '[Errno 30] Read-only file
system' on every file; he chmod 777'd and nothing changed — because EROFS is
the KERNEL refusing writes to a docker ':ro' volume mount, which no chmod
can fix. SoulSync's response was a wall of per-file warnings and a fix
result that still said success with a soft "(read-only?)" hint.
- apply_art_to_album_files now pre-flights the album folder with statvfs
(asks the kernel, writes nothing): a read-only mount short-circuits the
whole album instead of failing file by file. Belt: a per-file/cover EROFS
(overlay quirks where statvfs lies) still sets the flag.
- the repair worker's apply now FAILS the finding with the actual cure:
"remove ':ro' from the volume mapping and recreate the container — chmod
cannot change this". EACCES (a real permissions problem chmod CAN fix)
deliberately keeps the old soft path.
Tests: RO mount short-circuits before any file/cover write, save-time EROFS
still flagged, EACCES not conflated with EROFS. 29 art/repair tests pass.