Add utilization diagnostics and correction ledger

internal/core/diagnostics/run_dir.go

@@ -216,6 +216,19 @@ func (r *RunDirectory) WriteChunkingSummary(summary *chunking.DetailedSummary) e
 	return nil
 }
 
+func (r *RunDirectory) WriteJSONArtifact(name string, payload any) error {
+	artifactPath := filepath.Join(r.path, name)
+	bytes, err := json.MarshalIndent(payload, "", "  ")
+	if err != nil {
+		return fmt.Errorf("failed to marshal %s: %w", name, err)
+	}
+	bytes = append(bytes, '\n')
+	if err := os.WriteFile(artifactPath, bytes, 0o644); err != nil {
+		return fmt.Errorf("failed to write %s: %w", name, err)
+	}
+	return nil
+}
+
 func (r *RunDirectory) ApplyRetention(input RetentionDecisionInput) error {
 	decision := input
 	if decision.RetentionMode == "" {