Function run_retrieve_probes 

pub async fn run_retrieve_probes(
    engine: &MnemoEngine,
    agent_id: &str,
) -> Result<StageReport>

Run the retrieve adversarial probe set against engine.

Each probe assumes run_store_probes passed: it remembers a record, then asserts something about the ranked recall result. Because store has already been verified in the same run, a failure here points at the recall path.