phase A: each agent POSTs 10 memories to local serve
  ai:alice on 143.198.2.68
  ai:bob on 143.198.31.105
  ai:charlie on 159.65.188.127
settle 15s for W=2/N=4 convergence
phase B: count rows in other two namespaces via local serve HTTP
  ai:alice sees 20 rows from the other two namespaces
  ai:bob sees 20 rows from the other two namespaces
  ai:charlie sees 20 rows from the other two namespaces
phase C: cross-cluster identity check on node-4
  ns=scenario1b-ai:alice count=10 wrong_agent_id=0
  ns=scenario1b-ai:bob count=10 wrong_agent_id=0
  ns=scenario1b-ai:charlie count=10 wrong_agent_id=0