docs(acl): ADR-0019 + demo/backlog for zaak cancellation on timeout (S-10c) (refs #106)

Records the ZGW cancellation-modelling decision (distinct non-terminal
Geannuleerd status + Vervallen resultaat, resolved by name) and documents the
end-to-end timeout-cancellation path.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

docs/demo-script.md

@@ -461,4 +461,24 @@ make verify-acl        # → "Storing a diploma creates a real informatieobject
 `ProvideDocuments` → ACL `POST /documenten` → ZGW `enkelvoudiginformatieobjecten` +
 `zaakinformatieobjecten`; the wait is then completed and the case advances to Beoordelen (§8.1, ADR-0018).
 
-> Setting the ZGW zaak to a cancellation status on 30-day expiry is a follow-up (S-10c, #106).
+## S-10c — the ZGW zaak is cancelled when the document term lapses (#106)
+
+When the 30-day document term lapses (S-10a), the domain no longer only marks the aggregate `Verlopen` —
+it now also cancels the **ZGW zaak** through the ACL, so OpenZaak and the register agree. The zaak is set
+to a distinct, non-terminal **`Geannuleerd`** status with a **`Vervallen`** resultaat (as opposed to the
+approval `Afgehandeld` + `Geregistreerd`), resolved by name in the ACL (§8.1, ADR-0019).
+
+```bash
+# 1. The ACL integration test proves cancellation records the Geannuleerd status + a resultaat
+#    against a live OpenZaak:
+make verify-acl        # → "Cancelling a zaak records the geannuleerd status and a resultaat"
+#
+# 2. End-to-end: the domain check submits a registration, fires its 30-day timer early, and asserts
+#    the timeout worker both expires the registration (VERLOPEN) and cancels its zaak (Geannuleerd):
+make verify-domain     # → "the timed-out registration's zaak was cancelled to Geannuleerd in OpenZaak"
+```
+
+**The path:** Flowable P30D timer → `RegistratieVerlopen` job → domain `ExpireRegistrationWorker` → ACL
+`POST /annuleringen` → ZGW `resultaten` + `statussen` (Geannuleerd); the aggregate then moves to
+`Verlopen`. The ACL cancels the zaak **before** the aggregate is expired, so a failed ZGW call leaves the
+job for redelivery rather than diverging the two (ADR-0019).