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/mp4genre.go

@@ -7,15 +7,15 @@ import (
 	"strings"
 )
 
-// MP4 has the same gap as Vorbis comments (#2500). A tag writer stores several
-// genres as several "data" atoms inside one ©gen atom (mutagen and Picard do),
-// or occasionally as repeated ©gen atoms. dhowden/tag keeps atoms in a map keyed
+// MP4 has the same gap as Vorbis comments. A tag writer stores several genres
+// as several "data" atoms inside one ©gen atom (mutagen and Picard do), or
+// occasionally as repeated ©gen atoms. dhowden/tag keeps atoms in a map keyed
 // by name (mp4.go: m.data[name] = data), so one value survives either way.
 //
 // Path to the values: moov > udta > meta > ilst > ©gen > data. A file that
-// carries only the numeric "gnre" atom has no ©gen; this reader returns
-// (nil, nil) for it, and extractGenres falls back to dhowden/tag, which resolves
-// gnre to a name.
+// carries only the numeric "gnre" atom has no ©gen; this reader returns (nil,
+// nil) for it, and extractGenres falls back to dhowden/tag, which resolves gnre
+// to a name.
 
 // maxMP4GenreAtomSize caps how much of one ©gen atom is buffered. Genre text is
 // bytes; the cap only stops a corrupt size from making the scanner allocate.