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/scanrun.go

@@ -24,8 +24,8 @@ type LibraryStageTallies struct {
 	Updated int `json:"updated"`
 	Skipped int `json:"skipped"`
 	Errored int `json:"errored"`
-	// Reconcile results (#2523). Surfaced in the scan record because a track
-	// disappearing from the library is something the operator should be able to
+	// Reconcile results. Surfaced in the scan record because a track
+	// disappearing from the library is something an admin should be able to
 	// see happened, rather than discovering it when a mix comes up short.
 	Missing  int `json:"missing"`
 	Restored int `json:"restored"`
@@ -38,7 +38,8 @@ func (st Stats) tallies() LibraryStageTallies {
 	}
 }
 
-// MBIDBackfillStageTallies wires BackfillMBIDsResult into the scan_runs jsonb column.
+// MBIDBackfillStageTallies wires BackfillMBIDsResult into the scan_runs jsonb
+// column.
 type MBIDBackfillStageTallies struct {
 	Processed  int `json:"processed"`
 	Healed     int `json:"healed"`
@@ -46,7 +47,8 @@ type MBIDBackfillStageTallies struct {
 	Duplicates int `json:"duplicates"`
 }
 
-// CoverEnrichStageTallies wires EnrichBatch tallies into the scan_runs jsonb column.
+// CoverEnrichStageTallies wires EnrichBatch tallies into the scan_runs jsonb
+// column.
 type CoverEnrichStageTallies struct {
 	Processed int `json:"processed"`
 	Succeeded int `json:"succeeded"`
@@ -64,13 +66,12 @@ type ArtistArtEnrichStageTallies struct {
 // RunScanConfig assembles the knobs for the orchestrator. BackfillCap is
 // the album/artist-MBID-backfill batch cap (5000); EnrichCap /
 // ArtistEnrichCap gate cover/artist-art enrichment (0 = off, <0 =
-// unbounded — #388 removed the global cover-art cap; remote providers
-// self-throttle per provider).
+// unbounded; remote providers pace themselves).
 type RunScanConfig struct {
 	BackfillCap     int
 	EnrichCap       int
-	ArtistEnrichCap int    // M7 cover-sources: cap for the artist-art enrich stage
-	DataDir         string // M7 cover-sources: where to write artist-art files
+	ArtistEnrichCap int    // cap for the artist-art enrich stage
+	DataDir         string // where to write artist-art files
 }
 
 // RunScan is the unified scan-chain orchestrator. Creates a scan_runs row,
@@ -235,7 +236,8 @@ func RunScan(
 		}
 	}
 
-	// Finalize: set finished_at + error message (or empty string if all stages succeeded).
+	// Finalize: set finished_at + error message (or empty string if all stages
+	// succeeded).
 	errMsg := ""
 	if firstErr != nil {
 		errMsg = firstErr.Error()
@@ -243,7 +245,8 @@ func RunScan(
 	if ferr := q.FinishScanRun(ctx, dbq.FinishScanRunParams{
 		ID: row.ID, Column2: errMsg,
 	}); ferr != nil {
-		// Even the finalize failed; log loudly, return the original error if any.
+		// Even the finalize failed; log loudly, return the original error if
+		// any.
 		logger.Error("scan run finalize failed", "id", row.ID, "err", ferr)
 		if firstErr != nil {
 			return row.ID, firstErr