alice writes claim: "sky-color-adc0d8d6 is blue" on node-1
bob writes contradicting claim: "sky-color-adc0d8d6 is red" on node-2
  alice.id=caf258d1-f334-4270-afd0-32386b254325 bob.id=de7fd922-ff81-4225-ae22-b5a795af033e
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