alice writes claim: "sky-color-b54e9d29 is blue" on node-1
bob writes contradicting claim: "sky-color-b54e9d29 is red" on node-2
  alice.id=704cc9d5-7c14-4af1-a92c-2be49a4c56d6 bob.id=0686dd66-1268-4a3e-a7a1-308887d8eead
settle 10s for quorum fanout + contradiction indexing
charlie queries /api/v1/contradictions on node-3
  HTTP 200
  sees both memories: True; sees contradicts link: True