alice writes claim: "sky-color-ddacadf0 is blue" on node-1
bob writes contradicting claim: "sky-color-ddacadf0 is red" on node-2
  alice.id=866266d3-95d6-4b11-b68f-23abf7006bca bob.id=6126dccc-b71a-46ce-afe5-61490cd83742
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