Clicking a track row in the download modal now opens a polished detail modal
(its own template, webui/track-detail-modal.html, included into index.html;
behavior in static/track-detail.js): cover, title/artist/album, status badge,
in-app play, source, quality, AcoustID verdict, file location, and the
expected-vs-downloaded provenance — backed by /api/downloads/task/<id>/detail.
It adapts by status:
- completed -> play (library stream) + full provenance
- quarantined-> reason + Listen (quarantine stream) + Accept & Import + Search
- failed/not_found -> reason + Search
This absorbs the standalone quarantine chooser, which is removed (its
Listen/Accept/Search live here now, with the same Windows file-handle release
before Accept and the thin-sidecar -> Recover-to-Staging fallback). Plain
failed/not-found rows still go straight to the search modal; sync-import modal
unaffected. Status cells clear their clickable/detail state each render so a row
that flips to completed isn't left with a stale handler.
