the AcoustID scanner matched library_history rows by EXACT file_path, but that path is
frozen at import time while the file moves afterward (media-server import / reorganize) —
so tracks.file_path (what the scan reads) no longer equals it. two failures resulted, both
introduced in 37ea6604: verified status never reached the history row (verified tracks kept
showing 'unverified'), and a fresh acoustid_scan row was INSERTed every run (5551 rows for
3675 songs).
- new pure, tested matcher (core/downloads/history_match.py): exact path → filename guarded
by title; prefers a real download row over a synthetic scan row.
- _persist_status now HEALS the matched row's path + status (so future scans match cleanly),
DELETES synthetic acoustid_scan duplicates by exact path (collision-free, never a real row),
and inserts only when the file genuinely has no row.
- a full AcoustID job now self-cleans existing duplicates — no destructive bulk migration.
8 matcher + 4 real-DB heal/dedup/insert tests; existing scanner tests updated to the new
seam (heal vs insert). 1076 acoustid/verification/download tests green.
