Function run_verification_round 

pub async fn run_verification_round(
    keys: &[XorName],
    targets: &VerificationTargets,
    p2p_node: &Arc<P2PNode>,
    config: &ReplicationConfig,
) -> HashMap<XorName, KeyVerificationEvidence>

Send batched verification requests to all peers and collect evidence.

Implements Section 9 requirement: one request per peer carrying many keys. Returns per-key evidence aggregated from all peer responses.