List Agent or harness runs

Use agent__list_traces with an agent_... or harness_... handle.

Required input: subject_id.
Optional inputs: start_time_unix_seconds, end_time_unix_seconds, limit, cursor, sort, session_id, and Gateway’s rationale.
Limit: accepts 1 to 100.
Effect: read only.

Pass cursor back unchanged. For a subject the caller did not create, an empty result can mean the caller has not run it.