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/duplicate_survivor.go

@@ -18,15 +18,15 @@ type SurvivorCandidate struct {
 	TagFit int
 }
 
-// TagFitScore counts the signs that a copy belongs where it is filed (M498
-// #5436), one point each:
+// TagFitScore counts the signs that a copy belongs where it is filed, one
+// point each:
 //   - it has a track number that no other track on its album also claims
 //   - its file name carries no video-rip marker (SourceMarkersFor)
 //   - it has a MusicBrainz recording id
 //
 // Two copies of one song differ in these far more often than in anything a
-// listener hears: the Humanz rips differ by a few bytes, and file size picked
-// the wrong one in 6 of 21 groups.
+// listener hears: rips of one song can differ by a few bytes, which makes file
+// size a poor guide.
 func TagFitScore(hasTrackNumber, positionClash bool, filePath string, hasMBID bool) int {
 	score := 0
 	if hasTrackNumber && !positionClash {
@@ -48,13 +48,12 @@ func TagFitScore(hasTrackNumber, positionClash bool, filePath string, hasMBID bo
 var losslessFormats = map[string]bool{"flac": true, "wav": true}
 
 // ProposeSurvivor picks which copy of a duplicate group to keep, and gives the
-// reason in words the operator reads beside it. It is a default, not a verdict:
-// the report shows it and the merge (#3911) lets the operator choose another.
+// reason in words an admin reads beside it. It is a default, not a verdict:
+// the report shows it and the merge lets an admin choose another.
 //
 // In order:
 //  1. lossless over lossy — the one difference no later step can recover. It
-//     comes before tag fit: tags can be fixed, a deleted FLAC cannot, and on
-//     2026-10-20 five FLACs went for mp3s that only carried a recording MBID
+//     comes before tag fit: tags can be fixed, a deleted FLAC cannot
 //  2. the copy whose tags fit the album best (TagFitScore). It is zero for
 //     every copy when the caller does not know it, and the order falls through
 //     to the rules below