alice writes claim: "sky-color-c355ff02 is blue" on node-1
bob writes contradicting claim: "sky-color-c355ff02 is red" on node-2
  alice.id=68cb367b-ca68-4358-9847-dee9e5439017 bob.id=202342ef-5257-4b00-b39f-fc4a850a564c
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