alice writes claim: "sky-color-ced20b10 is blue" on node-1
bob writes contradicting claim: "sky-color-ced20b10 is red" on node-2
  alice.id=a6efaa3e-9cb3-44a2-b727-76d438f4d083 bob.id=f0f0a7e4-d592-4e1c-aa43-dd3d21487a22
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