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/architecture/adr-0019-zaak-cancellation-on-timeout.md

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+# ADR-0019: A timed-out zaak is cancelled with a distinct status + resultaat, resolved by name
+
+- **Status:** Accepted
+- **Date:** 2026-07-21
+- **Deciders:** Respellion engineering
+- **Relates to:** S-10c (#106). Completes the S-10a/S-10b boundary noted in ADR-0017 (§Consequences) and
+  reuses the ACL close-zaak machinery from S-09b (approval) and the Documenten work in ADR-0018.
+
+## Context
+
+ADR-0017 (S-10a) cancels the *process* and marks the domain aggregate `Verlopen` when the 30-day
+document term lapses, but explicitly deferred setting the ZGW **zaak** to a cancellation status. Left
+open, a timed-out zaak stays open in OpenZaak while the register shows the registration as lapsed — the
+two diverge. S-10c closes that gap: on expiry the domain must also cancel the zaak through the ACL
+(§8.1, the only code that talks to ZGW).
+
+The non-obvious part is *how to represent "cancelled" in ZGW* alongside the existing "approved" close.
+The approval path (S-09b) sets the zaak's **eindstatus** (the terminal statustype) plus a resultaat. In
+ZGW a zaaktype has exactly one eindstatus — the highest-`volgnummer` statustype — and setting it is what
+closes the zaak (`einddatum`). A second *terminal* status would collide with that single-eindstatus rule.
+
+## Decision
+
+**Model cancellation as a distinct, non-terminal `Geannuleerd` statustype plus a distinct `Vervallen`
+resultaat, and resolve both the approval and cancellation statustype/resultaat by their omschrijving
+(name) rather than by position or the eindstatus flag alone.**
+
+- **Seed.** `Geannuleerd` is seeded at `volgnummer` 2 — between `Ontvangen` (1) and the `Afgehandeld`
+  eindstatus (3) — so it is a *non-terminal* status and never displaces the eindstatus the approval path
+  resolves. A second resultaattype `Vervallen` (archiefnominatie `vernietigen`) is seeded beside the
+  approval `Geregistreerd` (`blijvend_bewaren`); both draw their `selectielijstklasse` from the
+  zaaktype's single `selectielijstProcestype` so they validate on publish.
+- **The ACL owns the mapping.** `OpenZaakGateway.SetZaakToCancellationStatusAsync` resolves `Geannuleerd`
+  + `Vervallen` by omschrijving and POSTs the resultaat then the status (OpenZaak requires a resultaat
+  before a closing/terminal status), mirroring `SetZaakToEindstatusAsync`. Exposed as
+  `AclService.CancelZaakAsync` behind the ACL endpoint `POST /annuleringen`. The omschrijvingen live as
+  constants in the gateway — the ACL, not the domain, knows which ZGW status means what (§8.1).
+- **Approval now resolves its resultaat by name too.** With two resultaattypen present, taking the first
+  is ambiguous (the Zaken API does not guarantee order), so the approval path resolves `Geregistreerd`
+  by omschrijving. Its statustype resolution is unchanged (still the eindstatus).
+- **Domain wiring.** The `ExpireRegistrationWorker` calls `IAclClient.CancelZaakAsync(zaakUrl)` **before**
+  advancing the aggregate to `Verlopen` (ACL-first, mirroring approval): if the ACL call fails the job is
+  redelivered (§8.6) rather than leaving the aggregate `Verlopen` with an open zaak. The existing
+  open-state guard stops a redelivered job from cancelling twice (a second resultaat would be a 400); a
+  registration that lapsed before its zaak was opened has nothing to cancel.
+
+## Consequences
+
+**Positive**
+
+- The domain aggregate and the ZGW zaak no longer diverge on timeout — both reflect the cancellation.
+- Reuses the approval close machinery (resultaat-then-status, ACL endpoint shape, ACL-first ordering), so
+  the change is additive and §8 stays clean (only the ACL talks to ZGW).
+- Verified at two levels: an ACL↔OpenZaak integration test asserts the live zaak reaches `Geannuleerd`
+  with a resultaat, and the domain verify script fires the real P30D timer and confirms the zaak is
+  cancelled end-to-end.
+
+**Negative / costs**
+
+- `Geannuleerd` is non-terminal, so the cancelled zaak's `einddatum` is not set — it carries a
+  cancellation status + resultaat but is not formally "closed" in ZGW. Accepted: the register reads the
+  domain aggregate's status, and a single eindstatus per zaaktype is a ZGW constraint we chose not to
+  fight. Formally closing a cancelled zaak (a second eindstatus, or reusing `Afgehandeld` with a
+  `Vervallen` resultaat) is a possible follow-up.
+- The ACL couples to the seeded omschrijvingen (`Geregistreerd`/`Geannuleerd`/`Vervallen`) by string
+  constants. This mirrors the existing implicit coupling to the catalogus (zaaktype URL, eindstatus) and
+  is documented in the gateway.
+- Renumbering `Afgehandeld` from `volgnummer` 2 to 3 means a *stale* local catalogus must have its
+  OpenZaak volumes reset for the change to take effect; CI reseeds a fresh catalogus each run.
+
+## Alternatives considered
+
+- **Shared eindstatus, distinct resultaat only** (reuse `Afgehandeld`, distinguish approval vs
+  cancellation purely by the resultaat). ZGW-idiomatic and would set `einddatum` on cancellation too, but
+  the register would show no visibly distinct cancellation *status*. Rejected in favour of the issue's
+  explicit "distinct statustype + resultaattype" outcome, which makes the cancellation legible in ZGW.
+- **A second terminal (eindstatus) `Geannuleerd`.** Rejected: ZGW allows only one eindstatus per
+  zaaktype (highest volgnummer); a second terminal status would either not close the zaak or collide with
+  the approval eindstatus resolution.
+- **Passing the target omschrijvingen from the domain.** Rejected: which ZGW status means "cancelled" is
+  ZGW vocabulary the ACL owns (§8.1); the domain says only "cancel this zaak".