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_classify.go

@@ -8,7 +8,7 @@ import (
 	"unicode"
 )
 
-// Duplicate classification (M498 #5435; settled further 2026-10-19).
+// Duplicate classification.
 //
 // A duplicate group is one recording found more than once. What should happen
 // to it depends on where the copies sit:
@@ -19,15 +19,15 @@ import (
 //     album it came from, a deluxe edition and the standard one, or one
 //     recording a later release retitled ("The Ragtime Cat", "F.O.D. (live)",
 //     a romanized title): each copy belongs to its own release, so none is
-//     deleted (unless it is a video rip; the resolver decides). The measured
-//     library (2026-10-19) had 451 such groups waiting on the operator under
-//     different titles, and they were retitles, not different songs.
+//     deleted (unless it is a video rip; the resolver decides). Copies under
+//     different titles on different releases are retitles, not different
+//     songs.
 //   - distinct: one album, two versions of a song that sound alike, named as
 //     such ("Lovesick", "Lovesick (Instrumental)"). Not duplicates.
 //   - mismatch: one album holds the same audio under different song titles:
 //     one file filling several track slots, a broken download. Which slot is
 //     right is the resolver's to decide from MusicBrainz's track lengths.
-//   - review: what none of these fits. The operator decides.
+//   - review: what none of these fits. An admin decides.
 
 // DuplicateClass is a group's shape. The values are duplicate_groups.class.
 type DuplicateClass string
@@ -54,8 +54,8 @@ type ClassifyMember struct {
 // adds to a title (featuring credits, remaster notes, video markers) and keeps
 // what names a different recording (live, demo, remix, instrumental). On one
 // album, titles that differ only by such a word are two versions (distinct)
-// unless the bytes are identical, which is one file twice: the #3885 case of
-// "WWW" and "WWW (instrumental)" holding the same file is a wrong slot.
+// unless the bytes are identical, which is one file twice: "WWW" and "WWW
+// (instrumental)" holding the same file is a wrong slot.
 func ClassifyDuplicateGroup(tier string, members []ClassifyMember) DuplicateClass {
 	if len(members) < 2 {
 		return ClassReview
@@ -136,7 +136,8 @@ func songKey(title, artist string) string {
 var (
 	// A bracketed credit: "(feat. Panda Bear)", "[ft. X]", "(featuring Y)".
 	featBracket = regexp.MustCompile(`(?i)[(\[][^)\]]*\b(feat\.?|ft\.?|featuring)\s[^)\]]*[)\]]`)
-	// A credit trailing the title without brackets: "Doin' It Right ft. Panda Bear".
+	// A credit trailing the title without brackets: "Doin' It Right ft. Panda
+	// Bear".
 	featTrailing = regexp.MustCompile(`(?i)\s(feat\.?|ft\.?|featuring)\s.*$`)
 	// "(2011 Remaster)", "[Remastered]", "- Remastered 2009".
 	remasterBracket = regexp.MustCompile(`(?i)[(\[][^)\]]*remaster[^)\]]*[)\]]`)
@@ -149,10 +150,11 @@ var (
 // whether two copies carry the same one.
 //
 // Dropped: a leading "Artist - " (a video upload's title), bracketed featuring
-// credits and remaster notes, and bracketed segments carrying a video-rip marker
-// ("(Official Video)", "[HD]"). Kept: every other bracketed word, so "(live)",
-// "(demo)", "(acoustic)", "(remix)" and "(instrumental)" still tell recordings
-// apart. Then case, "&" against "and", and punctuation and spacing are ignored.
+// credits and remaster notes, and bracketed segments carrying a video-rip
+// marker ("(Official Video)", "[HD]"). Kept: every other bracketed word, so
+// "(live)", "(demo)", "(acoustic)", "(remix)" and "(instrumental)" still tell
+// recordings apart. Then case, "&" against "and", and punctuation and spacing
+// are ignored.
 func MatchTitleKey(title, artist string) string {
 	t := strings.TrimSpace(title)
 	if a := strings.TrimSpace(artist); a != "" {