alice writes claim: "sky-color-272e6c94 is blue" on node-1
bob writes contradicting claim: "sky-color-272e6c94 is red" on node-2
  alice.id=68a666e9-d6ab-4dfd-8084-b532630def89 bob.id=845ce240-70c9-4e78-8949-312d62557d31
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