fix(036): timedelta import + emit_terminal status mapping + C5 decision memory

agent/src/ss_tools/agent/_run_tracker.py

@@ -166,10 +166,12 @@ class RunTracker:
         error_code: str | None = None,
         error_detail: str | None = None,
     ) -> None:
-        """Mark the run as COMPLETED, FAILED, or CANCELLED."""
+        """Mark the run as completed, failed, or cancelled.
+        Maps run-level status to lowercase event status for Pydantic validation."""
+        status_map = {"COMPLETED": "completed", "FAILED": "failed", "CANCELLED": "skipped"}
         await self.append_event(
             event_type="terminal",
-            status=status,
+            status=status_map.get(status, "completed"),
             payload={"error_code": error_code, "error_detail": error_detail},
         )