alice writes claim: "sky-color-5171468e is blue" on node-1
bob writes contradicting claim: "sky-color-5171468e is red" on node-2
  alice.id=2a171fb3-a3ee-4b32-8511-2da20d8e3857 bob.id=621c4ddc-7b75-45cc-ae69-09e381082634
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