alice writes claim: "sky-color-fe6520c8 is blue" on node-1
bob writes contradicting claim: "sky-color-fe6520c8 is red" on node-2
  alice.id=c6f8c2d5-1179-4d15-8962-700bbfdc47e5 bob.id=1ed7d523-610c-431c-9f9f-d42625d7e6f2
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