fix(auth): Hole 1 — bind agent sponsor to SSO-authenticated human, refuse workspace-key-set sponsors + hash-chained audit

[kjgbot]

Summary

• reject workspace-token callers that try to create a legacy/workspace-key-set sponsor identity
• refuse attestation grants for identities without an OIDC-bound human sponsor
• test both workspace-key sponsor forgery rejection paths
• document the Chief → OIDC sponsor proof → RelayAuth binding mechanism
• document the existing tamper-evident compliance ledger boundary

Root cause and impact

The sponsor API already verified an OIDC ID token and issued a short-lived RS256 sponsor proof, but legacy identity creation could still accept a sponsor selected by a workspace-key holder. Attestation issuance then trusted that legacy identity sponsorship. That allowed shared workspace-key holders to become indistinguishable in the evidence chain.

Identity creation now fails closed for workspace-token callers unless the organization requires OIDC sponsor binding and the caller supplies a valid RelayAuth sponsor proof. Attestation grant issuance independently requires the stored identity sponsor binding to be OIDC.

Audit Gap 3

The security evidence store already exists as attestation_ledger. It is append-only, has no update or retention deletion path, uses a per-organization SHA-256 prev_hash/entry_hash chain, and stores RS256-signed JWS entries. The separately retained audit_logs table remains the operational query feed and is explicitly not treated as the write-once evidence ledger. No redundant migration was added.

Validation

• full RelayAuth server test suite: passed
• focused attestation and OIDC sponsor-binding tests: 24 passed, 0 failed
• git diff --check: passed

Known repository baseline

The monorepo build reaches an existing TypeScript package-boundary error because @relayauth/migrate does not emit a declaration file consumed by the server package. The server tests, including the new security coverage, pass.

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