`/api/musicbrainz/search_tracks` powers the Fix popup's auto-search
cascade for users on MusicBrainz as primary. When both track + artist
fields were filled, `search_tracks_with_artist` always took the bare
keyword path (`<track> <artist>` joined as one query string). MB's
recording-search scorer weights title matches far above artist matches,
so for "Coffee Break" + "Zeds Dead" the top results were Emapea / The
Vidalias / West One Orchestra's "Coffee Break" — three unrelated cover-
title collisions ahead of the canonical Zeds Dead recording. The
endpoint's `rerank_tracks` pass can't fix this when the right answer
is below the API's 50-result cutoff.
Both-fields mode now uses a strict field-scoped Lucene query first
(`recording:"<t>" AND artist:"<a>"`) which anchors the artist and
prunes title-collision covers at the source. `min_score=0` because the
field-scoped query is itself precise; rerank still does final ordering.
Bare query stays as the fallback when strict returns nothing — covers
the diacritic / alias cases the original `strict=False` path was added
for ("Bjork" query vs canonical "Björk" artist where Lucene phrase
match never hits the recording).
Single-field mode (track-only or artist-only) is unchanged: still bare-
query directly, since there's no artist value to anchor.
Also stable-sort results to prefer entries with non-zero `duration_ms`.
MB has multiple recordings per song (single release, album release,
remasters, compilations) and not every recording carries length data.
Without the preference sort, the user sees a 0:00 row first while a
sibling recording with the real 3:04 sits two rows below — matches the
report where MBID-paste lookup of the canonical recording (length 3:04)
contradicted the search-result's 0:00 row for the same song.
Tests:
- new `test_search_tracks_with_artist_strict_first_when_both_fields`
pins the strict=True call when both fields present
- new `test_search_tracks_with_artist_falls_back_to_bare_when_strict_empty`
pins the Björk-style fall-through path
- new `test_search_tracks_with_artist_prefers_results_with_known_length`
pins the length-preference sort
- existing `..._keeps_low_score_for_rerank` updated to side_effect so
the bare-fallback path is exercised; behaviour pinned identically
- existing `..._uses_bare_query_mode` renamed + repurposed for strict-
first; old name's behaviour no longer accurate
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