Backfill action bound audit grouped metrics metadata

workspace/runs/action_bound_audit_rgb_refs/metrics_by_seed.json

@@ -0,0 +1,6 @@
+{
+  "_artifact_backfill": true,
+  "_grouping": "seed",
+  "_note": "Original grouped metrics were absent. This placeholder is explicit metadata, not a computed scientific result.",
+  "_run_dir": "runs/action_bound_audit_rgb_refs"
+}

workspace/runs/action_bound_audit_rgb_refs/metrics_by_task.json

@@ -0,0 +1,6 @@
+{
+  "_artifact_backfill": true,
+  "_grouping": "task",
+  "_note": "Original grouped metrics were absent. This placeholder is explicit metadata, not a computed scientific result.",
+  "_run_dir": "runs/action_bound_audit_rgb_refs"
+}