issue_agent_credential
Returns agent_key once, key_fingerprint, allowed rails, scopes, and audit event.
Agents call this surface to receive scoped credential envelopes. Each credential carries allowed rails, scopes, fingerprint, masked key hint, rotation state, and audit event ID.
Credential objects bind agent_id, allowed_rails, scopes, key_fingerprint, masked_key_hint, and rotation state.
Returns agent_key once, key_fingerprint, allowed rails, scopes, and audit event.
Returns old key ID, new key ID, new fingerprint, and rotation event.