Fixes the 'cancelled but still shows running' stuck bug and adds real depth:
- classify_state now distinguishes 'cancelled' from 'failed'.
- Monitor is robust to slskd forgetting a transfer: if it's gone, it first tries to
complete from the FILE on disk (survives the music 'Clean Completed Downloads'
auto-clear), else counts misses and fails the row after ~8 polls instead of hanging
on 'downloading' forever. Cancelled transfers → cancelled status.
- POST /downloads/cancel (slskd DELETE transfer + mark cancelled) and /downloads/retry
(re-grab the same release). get_video_download(id) added; clear includes cancelled.
process_download stays pure (fs/slskd injected); 15 tests, ruff + guard clean.
Phase B (page: tabs/queue/history/cancel+retry buttons) next.
Phase 2 — the engine:
- core/video/download_monitor.py: a daemon thread polls slskd for active video
downloads, updates progress, and on completion MOVES the file from the shared
download folder into the per-type library folder + marks it completed. The
per-download decision (process_download) is pure (fs + slskd injected) — 6 tests.
- POST /downloads/grab: validates (Soulseek-only v1), resolves the target library by
kind, starts the slskd download, records the row, lazily starts the monitor.
- GET /downloads/active (list + ensure monitor running) · POST /downloads/clear
(drop finished).
14 tests, isolation guard + ruff clean. Grab button + Downloads page next.
