- Imported tracks are created directly under their final name with
O_EXCL (never overwriting; " (2)" on conflict), fsync'ed and checked
against SHA-256 — no hidden .pipu-tmp file next to them any more.
- On any failure the agent removes its own partial file and the empty
directories it created for it.
- The write check uses access(W_OK) and the read-only mount flag instead
of creating and deleting .pipu-write-test in the storage root.
- Tests assert the storage tree holds only audio files after successful
and failed writes and after the write check.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
