alice writes claim: "sky-color-ac9a41d8 is blue" on node-1
bob writes contradicting claim: "sky-color-ac9a41d8 is red" on node-2
  alice.id=ecde7b3a-7a16-4113-a809-b0822de9715c bob.id=3db74173-6926-4fec-9adf-4e99109b120e
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