alice writes claim: "sky-color-557de01d is blue" on node-1
bob writes contradicting claim: "sky-color-557de01d is red" on node-2
  alice.id=91efbae4-1513-4684-b749-afb6679602cc bob.id=ea19c9e8-75c6-4acc-85f3-649a15fe3d1c
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