alice writes claim: "sky-color-95b11a17 is blue" on node-1
bob writes contradicting claim: "sky-color-95b11a17 is red" on node-2
  alice.id=4deb0dc3-e704-47cf-a4c4-6b04ae472376 bob.id=77577240-62b2-4b41-96e2-0ddfd0219353
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