alice writes claim: "sky-color-3791aede is blue" on node-1
bob writes contradicting claim: "sky-color-3791aede is red" on node-2
  alice.id=a1a82ca5-ee5a-4dc1-9e72-27098762c3b7 bob.id=3572cc8b-1c4f-4a70-bebf-b06452423cf5
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