Register a merchant public key for UCP terms verification

An organization API key. Its scopes decide what it may call; decision:shadow is the narrowest: SHADOW evaluations through POST /v1/authority/grants or its alias POST /v1/authority/enforce-and-bind only (DECISION_SHADOW_MODE_DENIED in any other mode; DECISION_SHADOW_FIELD_DENIED for a body carrying context.decionis_policy, evidence or escalation), with no integration dispatch. A key whose only scope is decision:shadow (an AgentSafe hosted gateway's) reaches exactly those two, POST /v1/auth/credential-context, POST /v1/hosted-gateway/keys/confirm and POST /v1/hosted-gateway/keys/revoke-self; every other route answers 403 HOSTED_GATEWAY_KEY_PATH_DENIED. decision:enforce is an enforced hosted gateway's key: evaluations in SHADOW or ENFORCEMENT through POST /v1/authority/grants or its alias (400 DECISION_ENFORCE_FIELD_DENIED for a body carrying context.decionis_policy; it never holds policy:write), and the grants and managed escalations they bind. A key whose scopes are decision:enforce (with or without decision:shadow) reaches exactly POST /v1/authority/enforce-and-bind, POST /v1/authority/grants, GET /v1/authority/grants/{grant_id}, POST /v1/authority/grants/{grant_id}/claims, POST /v1/authority/grants/{grant_id}/receipts, POST /v1/authority/grants/{grant_id}/reconciliations, POST /v1/execution/verify-token, POST /v1/execution/claim-token, POST /v1/execution/consume-token, POST /v1/execution/finalize-token, GET /v1/authority/escalations/{escalation_id}, DELETE /v1/authority/escalations/{escalation_id}, POST /v1/auth/credential-context, POST /v1/hosted-gateway/keys/confirm and POST /v1/hosted-gateway/keys/revoke-self, each id a UUID; every other route answers 403 HOSTED_GATEWAY_KEY_PATH_DENIED.

In: header