no_people_found releases the
hold. Poll, History and webhook expose the same billing snapshot.
GET /v1/account for Balance/Reserved/Available and effective limits. Use
cursor-paginated GET /v1/credits for immutable minor-unit events. Every
reserve/capture/release carries its durable job or People Search subject.
An estimate remains available even when Available is zero. Confirmation locks
the wallet and revalidates all concurrent holds; insufficient Available returns
402 insufficient_available_credits with the current wallet, required amount,
and shortfall, without creating a job or partial reservation.