alice writes claim: "sky-color-b524049e is blue" on node-1
bob writes contradicting claim: "sky-color-b524049e is red" on node-2
  alice.id=7427f51e-a114-428a-8a19-c1680ec4c4ce bob.id=3dff9270-7247-49fa-adc8-84744210bc1f
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