Per the original intent, "Sync" is now a single-artist deep scan: it uses the SAME
reconciliation source as the whole-library deep scan instead of a separate
disk-existence check.
- Phase 1 already calls the deep-scan worker's _process_artist_with_content; now it
passes seen_track_ids so the pull collects the server's current track IDs for the
artist (existing + new), exactly as the library deep scan does.
- Phase 2 stale = (artist's DB tracks for this server) − seen, then
delete_stale_tracks(server_source) — identical mechanism to deep scan, scoped to
one artist. The old os.path.exists disk check (which could mass-delete on an
unreachable mount) is gone.
- Removal only runs when the server pull SUCCEEDED — no trustworthy 'seen' set
(no server, unreachable, or a failed pull) → skip, never delete. The
is_implausible_stale_removal guard (>50% unseen) stays as the same safety net
deep scan has for a flaky response. @admin_only retained.
Tests rewritten for the server-diff model: removes only tracks the server no longer
has; guard skips when most are unseen; a failed pull skips removal entirely;
admin-only. 8 tests pass.
d82d02b921
