Moves an unresolved content record to an existing or new entity. Creates identity links, stores raw payload, writes traits to Postgres, and deletes from unresolved pool.

Conflict checking: If an identity link already exists on a different entity than the requested one, returns 409 IDENTITY_CONFLICT. Caller must merge entities first, then resolve.

{
  "unresolvedContentId": "01HXYZ123456789ABCDEFGH",
  "entityId": "01HXYZ123456789ABCDEFGI"
}

{
  "data": {
    "entityId": "01HXYZ123456789ABCDEFGI",
    "contentId": "01HXYZ123456789ABCDEFGJ",
    "identityLinksCreated": 1,
    "traitsWritten": 2
  }
}