alice writes claim: "sky-color-7885af77 is blue" on node-1
bob writes contradicting claim: "sky-color-7885af77 is red" on node-2
  alice.id=9de7ca45-777c-4b1f-826c-3d76e52d3847 bob.id=ed0e6bf5-60b0-463e-bd31-ce5f46fdb730
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