docs: library comments say what the scanner and resolver do, not how they came to be (#6277)

Rewrites the internal/library comment blocks to rule 32. Task, milestone,
decision and rule ids are gone; the incidents behind them are restated as
the constraint they left (why a file is deleted before its row, why the
missing mark is a mark, why duplicates block on duration). Counts and
album names from one library are dropped from production comments; test
comments keep the names their fixtures use. The tagReadVersion log keeps
each version's before and after, without the measurements.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

internal/library/acoustid_lookup_test.go

@@ -24,8 +24,8 @@ func cand(id, title string, sec int, score float64) acoustid.Candidate {
 	return acoustid.Candidate{Recording: acoustid.Recording{ID: id, Title: title, DurationSec: sec}, Score: score}
 }
 
-// D5, as a table over what decides it: how many candidates clear the
-// threshold, and whether title and length leave exactly one of them.
+// chooseRecording, as a table over what decides it: how many candidates clear
+// the threshold, and whether title and length leave exactly one of them.
 func TestChooseRecording(t *testing.T) {
 	const (
 		minScore = 0.85
@@ -154,7 +154,7 @@ func addTrack(t *testing.T, q *dbq.Queries, album dbq.Album, artist dbq.Artist,
 	return tr
 }
 
-// D4: the file's tag outranks a lookup, in both directions. Falsified by
+// The file's tag outranks a lookup, in both directions. Falsified by
 // restoring `mbid = EXCLUDED.mbid` in UpsertTrack: the first re-read below
 // then erases the looked-up id.
 func TestUpsertTrack_KeepsALookedUpMbidUntilATagCarriesOne_Integration(t *testing.T) {
@@ -302,7 +302,7 @@ func TestAcoustIDLookup_StopsWhenTheServiceCannotAnswer_Integration(t *testing.T
 	}
 }
 
-// The point of the milestone (#3921): once a lookup fills an MBID, the
+// The point of the lookup: once it fills an MBID, the
 // similarity worker picks the track as a seed and can map ListenBrainz's
 // answers back to it.
 func TestAcoustIDLookup_FilledTrackReachesSimilarity_Integration(t *testing.T) {
@@ -352,7 +352,7 @@ func TestAcoustIDLookup_FilledTrackReachesSimilarity_Integration(t *testing.T) {
 
 	// And it is reachable as a target: an answer cached for another seed
 	// before the lookup filled the MBID now resolves to it, with no new
-	// fetch (#5296).
+	// fetch.
 	other, _, _ := seedTrack(t, pool, filepath.Join(dir, "other.mp3"))
 	if _, err := pool.Exec(ctx, `INSERT INTO listenbrainz_similar_recordings (seed_track_id, recording_mbid, score)
 		VALUES ($1, 'rec-played', 0.8)`, other.ID); err != nil {