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/genre.go

@@ -33,7 +33,7 @@ func extractGenres(meta tag.Metadata, rs io.ReadSeeker) (genres []string, fellBa
 		// dhowden/tag will have nothing either — not worth flagging.
 		fellBack = meta.Genre() != ""
 	case tag.VORBIS, tag.MP4:
-		// dhowden/tag keeps only the last of a repeated field here (#2500):
+		// dhowden/tag keeps only the last of a repeated field here:
 		// see vorbisgenre.go and mp4genre.go.
 		var values []string
 		var err error
@@ -84,9 +84,8 @@ func normaliseGenres(values []string) []string {
 // A value may be:
 //   - plain text ("Alternative Rock") — passed through
 //   - a bare ID3v1 index ("17") — resolved to "Rock". This is what the spec
-//     says a numeric TCON means, and what ffmpeg does. It is why the operator's
-//     library showed genres like "4017" and "526617": several numeric values
-//     welded together by the old reader.
+//     says a numeric TCON means, and what ffmpeg does. Several of them
+//     welded together read as genres like "4017".
 //   - ID3v2.3 refinement syntax ("(17)", "(51)(39)", "(17)Hard Rock", "(RX)")
 //     — each parenthesised index becomes its own genre, and trailing text
 //     becomes one more.
@@ -134,7 +133,8 @@ func normaliseGenreValue(v string) []string {
 	}
 	if n, err := strconv.Atoi(v); err == nil {
 		if name, ok := id3v1GenreName(n); ok {
-			// Canonical table name, deliberately NOT re-cased — see id3v1Genres.
+			// Canonical table name, deliberately NOT re-cased — see
+			// id3v1Genres.
 			return append(out, name)
 		}
 		return out
@@ -143,8 +143,7 @@ func normaliseGenreValue(v string) []string {
 }
 
 // genreAcronyms are tokens that belong in caps. Tag editors that title-case the
-// whole genre field turn "EDM" into "Edm" and "UK Garage" into "Uk Garage", and
-// the operator's library carries all of these (#2468).
+// whole genre field turn "EDM" into "Edm" and "UK Garage" into "Uk Garage".
 //
 // Matched case-INSENSITIVELY, so "edm", "Edm" and "EDM" all land on "EDM". That
 // is a deliberate, narrow exception to the project's rule that genre case is
@@ -169,8 +168,8 @@ var genreAcronyms = map[string]string{
 // how "Children's Music" became "Children'S Music".
 //
 // Deliberately a fixed list rather than "lowercase whatever follows an
-// apostrophe": that broader rule would break "O'Brien" and "D'Angelo", which are
-// correctly capitalised after the apostrophe.
+// apostrophe": that broader rule would break "O'Brien" and "D'Angelo", which
+// are correctly capitalised after the apostrophe.
 var contractionSuffixes = map[string]bool{
 	"s": true, "t": true, "re": true, "ll": true, "ve": true, "d": true, "m": true,
 }
@@ -178,7 +177,7 @@ var contractionSuffixes = map[string]bool{
 // trueUpCasing repairs casing damage done by tag editors that title-case the
 // genre field. It only ever changes case, never the letters — so it cannot
 // silently turn one genre into a different one, which is what separates it from
-// the label-remapping idea #2468 rejected.
+// remapping labels.
 func trueUpCasing(s string) string {
 	if s == "" {
 		return s