alice writes claim: "sky-color-c1663257 is blue" on node-1
bob writes contradicting claim: "sky-color-c1663257 is red" on node-2
  alice.id=af3263b7-af79-4c32-a699-587822b9ed3d bob.id=96e17265-0023-4bc8-b011-fba26028dab4
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