alice writes claim: "sky-color-c8f7de4b is blue" on node-1
bob writes contradicting claim: "sky-color-c8f7de4b is red" on node-2
  alice.id=15aea9a1-1fad-4b22-8fb2-ed0b89e93921 bob.id=41d4d61f-2bfe-4d29-911e-f0a7eabcac59
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