Sponsor allows one verb once

Sponsor token (writ_sp_...) required — not the API key. The human sponsor approves a single write: the grant is scoped to the sponsor’s tenant and matches only checks from that tenant’s keys on all five fields (sponsor, agent, verb, target, purpose). Grants are single-use: the first matching check spends the grant; a second identical check needs a new grant. ttlSeconds defaults to 90 and must be between 1 and 3600. This is the approval behind every STEP_UP decision — the agent stops, the sponsor grants, the agent re-checks.