Live smoke against `/api/musicbrainz/search_tracks?track=Coffee+Break&artist=Zeds+Dead`
exposed the edge case the tiebreaker implementation couldn't reach:
The canonical Zeds Dead "Coffee Break" recording (mbid 6e2d4a70, length
184000ms) lives on the Coffee Break Single release — album_type='single',
which carries a 0.85 album_type_weight in `score_track`. A sibling
length-less recording (mbid 3b89bf3c) lives on an Album release —
album_type='album', weight 1.0. After multiplying by EXACT_ARTIST_BOOST
the canonical sat at 1.275 while the length-less sibling sat at 1.5.
The previous tiebreaker only kicked in on equal scores, so the
length-less album edition wins and the user sees 0:00 first instead of
the actionable 3:04 row. Bug reproduced: ordering came out
length-less / canonical / Omar-LinX-collab.
Switched `prefer_known_duration` to a 1.25x score boost on recordings
with non-zero duration_ms. The multiplier is sized above the
album-vs-single weight spread (0.176) so length-known recordings can
overcome an album-type penalty when scores would otherwise tie on
title + artist match, but stays small enough that cover/karaoke
penalty (0.05) and variant-tag penalty (0.85) still dominate — a
length-known tribute still loses to a length-less canonical.
Post-fix live response: 6e2d4a70 (canonical, 184000ms) sits first,
8ec2ce3f (Zeds Dead + Omar LinX collab, 153000ms) second, 3b89bf3c
(length-less album edition) third.
Verified Björk diacritic fallback path unaffected — `Bjork` + `Army of
Me` still cascades strict-empty → bare and returns all 10 Björk
recordings.
122 metadata tests pass — the three `prefer_known_duration` cases were
designed to pin behaviour, not the specific multiplier value, so they
all still pass under the boost implementation: ties promote
length-known, relevance still beats length-pref, default-off behaviour
unchanged.
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