Remove dead attribution_records helper with zero callers

src/tracegrad/attribute.py

@@ -20,7 +20,7 @@
 from concurrent.futures import ThreadPoolExecutor
 from dataclasses import dataclass, field
 from pathlib import Path
-from typing import Callable, Mapping, Sequence
+from typing import Callable, Sequence
 
 from pydantic import ValidationError
 
@@ -511,20 +511,6 @@ def _health(
     return HealthSample(sampled=sampled, agreed=agreed)
 
 
-def attribution_records(run: AttributionRun) -> list[Mapping[str, object]]:
-    """Serialize an attribution run for the ledger."""
-
-    return [
-        {
-            "trace_id": item.trace_id,
-            "cached": item.cached,
-            "error": item.error,
-            "result": item.result.model_dump(mode="json") if item.result else None,
-        }
-        for item in run.attributions
-    ]
-
-
 def instrument_summary(instrument: Instrument) -> str:
     """A one-line human description of the instrument in use."""