alice writes claim: "sky-color-4a10c381 is blue" on node-1
bob writes contradicting claim: "sky-color-4a10c381 is red" on node-2
  alice.id=eb77d5f3-fec0-4dd1-b0aa-13281c68baef bob.id=550debe2-e760-4a09-8844-5f5b949390e3
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