alice writes claim: "sky-color-c1a2c449 is blue" on node-1
bob writes contradicting claim: "sky-color-c1a2c449 is red" on node-2
  alice.id=bed0bcd2-3a32-4ae0-af52-8e21cc4f1022 bob.id=a5cf6113-099c-4475-8e61-894166f2c91c
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