phase A: ai:alice writes handoff to ai:bob (uuid=h-9cf8c10d8d4644a485975924e88a8398)
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-1ce0abd52079476aab3b09604cb2e239)
settle 8s for reverse-direction fanout
phase D: ai:alice reads ack on node-1
  ai:alice sees 1 ack memories from ai:bob