The 409 on a second subtitle for one language now comes from §15's
invariant rather than from the sidecar filename, so a provider fetch is
refused even when the language is held by a `.mt.srt` the path check
cannot see. The message names the manual delete as the way to replace
it. `claim_path` stays: two `media_files` rows for one video still
derive the same name from different ids.
Miguel Palhas
3122d5b0a0