CMRT 29: Threshold pref, cache-hit grouping fix, reanalyze fingerprint reset, lookup timestamp fix, redundant quality score fixes

[Swarnadip-Kar]

Five small, independent fixes bundled into one PR

A — Match threshold preference

FingerprintMatcher's 90% match cutoff was a compile-time constant. It's now
read from a new Preferences > Fingerprint Analysis spin box
(kCmrtMatchThresholdConfigKey, default 90%, stored as a 0.0-1.0 fraction).
FingerprintMatcher::compare() takes the threshold as a parameter; it has no
UserSettings dependency of its own. CmrtGroupingService re-reads the pref on
every processTrack() call so a change takes effect without restarting Mixxx.

B — Cache hits never triggered grouping

processJob()'s cache-hit branch wrote the MBID to the library table but
skipped CmrtGroupingService::processTrack() entirely -- only fresh network
lookups triggered grouping. Exact-duplicate files whose second copy resolved
via acoustid_cache would get tagged but never grouped. Fixed by calling
processTrack() in both branches.

C — Reanalyze silently skipped fingerprint data

AnalyzerChromaprint::initialize() skips any track with a still-valid
fingerprint_metadata row -- by design, so normal analysis doesn't redo
fingerprinting. But Reanalyze (all three variants) never cleared that row, so
reanalyzing a track whose audio had actually changed left the stale
fingerprint, .chroma file, and CMRT group membership untouched. Extracted the
existing fingerprint-clear loop into clearFingerprintDataForSelection() and
call it from all three Reanalyze slots (and reused it in slotClearFingerprint
and slotClearAllMetadata, removing the prior duplication).

D — acoustid_lookup_at never written

Column has existed in the schema since revision 41; TrackDAO::updateAcoustIdResult()
never included it in the UPDATE. Now stamped with the current Unix timestamp
inside the DAO, matching how TrackFingerprintDao already handles
computed_at/queued_at -- no new parameter, no call-site changes.

E — Add TrackFingerprintDao::getMemberQualityScore()

cmrt_members.quality_score is written once per track, when it joins a group
as a member or canonical (addCmrtMember(), called from createNewGroup(),
assignToExistingGroup(), and replaceCanonical()).

Add getMemberQualityScore(trackId), a structural twin of
updateMemberOffset(): same guard clause, same WHERE track_id=:track_id,
SELECT instead of UPDATE. Returns the same -1.0 "not yet scored" sentinel
CmrtMember::qualityScore and addCmrtMember() already use.

F — replaceCanonical() re-scoring a track it was already given the score for

handleMatchedCandidate() scores the new track once to decide whether it should
replace the existing canonical. When it does, replaceCanonical() was re-reading
TrackQualityInfo and re-running QualityScorer on that same track to fill in its
CmrtMember row -- same input, same output, computed twice for no reason.
replaceCanonical() now takes newCanonicalQualityScore as a parameter and the
caller passes through the value it already has, matching the pattern
assignToExistingGroup() already used.

G — handleMatchedCandidate() re-scoring the canonical on every match into its group

handleMatchedCandidate() re-derived the existing
canonical's score from TrackQualityInfo on every new track that matched into
that group, instead of reusing the score already stored in
cmrt_members.quality_score from when that track became canonical. Added
TrackFingerprintDao::getMemberQualityScore() (DAO commit) and switched
handleMatchedCandidate() to use it, falling back to the old recompute path
only if the canonical somehow has no stored score (call-site commit).

Depends on: cmrt-canonical-reelection (#37)

[coveralls]

Coverage Report for CI Build 28433425207

Coverage decreased (-4.2%) to 30.301%

Details

• Coverage decreased (-4.2%) from the base build.
• Patch coverage: 56 uncovered changes across 7 files (0 of 56 lines covered, 0.0%).
• 5 coverage regressions across 5 files.

Uncovered Changes

File	Changed	Covered	%
src/library/dao/trackfingerprintdao.cpp	25	0	0.0%
src/musicbrainz/cmrtgroupingservice.cpp	12	0	0.0%
src/widget/wtrackmenu.cpp	7	0	0.0%
src/preferences/dialog/dlgpreffingerprint.cpp	5	0	0.0%
src/musicbrainz/acoustidworker.cpp	3	0	0.0%
src/musicbrainz/fingerprintmatcher.cpp	3	0	0.0%
src/library/dao/trackdao.cpp	1	0	0.0%

Coverage Regressions

5 previously-covered lines in 5 files lost coverage.

File	Lines Losing Coverage	Coverage
src/library/dao/trackfingerprintdao.cpp	1	0.78%
src/musicbrainz/cmrtgroupingservice.cpp	1	0.0%
src/preferences/dialog/dlgpreffingerprint.cpp	1	0.0%
src/track/track.cpp	1	61.82%
src/widget/wtrackmenu.cpp	1	0.0%

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Coverage Stats

Relevant Lines:	116752
Covered Lines:	35377
Line Coverage:	30.3%
Coverage Strength:	59013.22 hits per line

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💛 - Coveralls