S-10c: expiring the aggregate to VERLOPEN is not enough — the ZGW zaak must also be cancelled through the ACL (§8.1). Adds IAclClient.CancelZaakAsync and its client/fakes, and asserts the worker cancels a still-open registration's zaak but leaves an already-resolved one untouched. Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>