phase A: ai:alice writes handoff to ai:bob (uuid=h-c38050104d9b4ff8aa4455771ea46fc7)
settle 8s for quorum fanout
phase B: ai:bob reads handoff on node-2
  ai:bob sees 1 handoff memories from ai:alice
phase C: ai:bob writes acknowledgement (uuid=a-aee7399a0a1f4a498e85400796bc1990)
settle 8s for reverse-direction fanout
phase D: ai:alice reads ack on node-1
  ai:alice sees 1 ack memories from ai:bob