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/fingerprint_scan_test.go

@@ -193,9 +193,10 @@ func TestScanner_FingerprintsOnlyNewOrChangedBytes_Integration(t *testing.T) {
 		t.Fatalf("rejected file stored %+v, want both halves NULL at version %d", got, fingerprintVersion)
 	}
 
-	// 6. With fingerprinting off (#3913) the scan decodes nothing. It still asks
-	// for the stream hash — a demux, and what recognises a moved file — but stores
-	// no row, and a changed file's old row goes: it describes bytes that are gone.
+	// 6. With fingerprinting off the scan decodes nothing. It still asks
+	// for the stream hash — a demux, and what recognises a moved file — but
+	// stores no row, and a changed file's old row goes: it describes bytes that
+	// are gone.
 	result = fingerprintResult{streamSHA256: sum, chromaprint: chroma}
 	off := DefaultFingerprintSettings
 	off.Enabled = false