When a downloader went offline holding a 'canceling' (or 'pausing') task, the
stale-lease recovery only requeued [assigned,downloading,uploading,interrupted]
— so the control task was never resolved and sat in 'canceling' forever, since
no live downloader would ever ack it.
recoverStaleDownloaderAssignments now also settles control states for stale
downloaders: canceling→canceled (terminal, assignment cleared) and
pausing→paused (resumable). Adds the resolveControlAssignedToMany repo method.
Integration test: a stale downloader's canceling task settles to canceled once
recovery runs.
Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
