fix(profiling): normalize timing metrics before export

tests/scripts/test_model_profiling.py

@@ -220,3 +220,25 @@ def test_deterministic_forward_artifacts_preserve_policy_mode(tmp_path):
     assert payload["reference_batch_size"] == 2
     assert "operator_fingerprint" in payload
     assert payload["outputs"]["loss"]["numel"] == 1
+
+
+def test_step_timing_collector_accepts_metric_like_values(tmp_path):
+    from lerobot.utils.profiling_utils import StepTimingCollector
+
+    class _MetricLike:
+        def __init__(self, val):
+            self.val = val
+
+    collector = StepTimingCollector()
+    collector.record(
+        forward_s=0.1,
+        backward_s=0.2,
+        optimizer_s=0.3,
+        total_update_s=_MetricLike(0.6),
+    )
+    collector.record_dataloading(_MetricLike(0.05))
+    collector.write_json(tmp_path / "step_timing_summary.json")
+
+    payload = json.loads((tmp_path / "step_timing_summary.json").read_text())
+    assert payload["total_update_s"]["mean"] == 0.6
+    assert payload["dataloading_s"]["mean"] == 0.05