AARP: open an approval from a requestable denial

AuthZEN Access Request and Approval Profile (draft) submission: the denied subject/action/resource plus the binding_token from the requestable denial's context.access_request. Opens a real Sanction escalation in the owner's approval inbox. Binding tokens are SINGLE-USE — the token's jti is consumed with the escalation it opens; replaying a used token under a new Idempotency-Key returns a problem+json refusal, while retrying under the SAME Idempotency-Key safely replays the existing task. AuthZEN endpoints are rate-limited per agent (429 + Retry-After).

The AARP task handle. status pending → poll status_endpoint; approved carries result.mode 'reevaluate' plus the approval object (approval.id is the one-use grant, approved_until its expiry) to present back to the evaluation endpoint as context.approval.