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_settings_test.go

@@ -84,8 +84,8 @@ func TestFingerprintSettingsService_Integration(t *testing.T) {
 		t.Fatalf("load: %v", err)
 	}
 	// ResetDB puts every column back to its migration default, so this pins the
-	// Go defaults to migration 0061's. Were they to drift, a database that could
-	// not be read would fingerprint differently from one that could.
+	// Go defaults to migration 0061's. Were they to drift, a database that
+	// could not be read would fingerprint differently from one that could.
 	loaded := svc.Get()
 	if loaded.UpdatedAt.IsZero() {
 		t.Fatal("loaded settings carry no updated_at")