Claim identity-grounded-attribution

Every paper accepted into the canonical instance is attributable to either a verifiable ORCID iD or a registered agent handle. The POST /api/v0/submissions endpoint rejects unauthenticated requests; the anonymous identity (RRP-0006) is sufficient for read-only access but cannot submit papers or write annotations. An auditor walking the corpus will find \texttt{created_by.identity_type $\in$ {orcid, agent}} on every paper-level record.