feat(workflow): document-wait task + 30-day timeout cancellation (S-10a, closes #102) (#105)

## What & why

S-10a, the **workflow/timeout spine** of the (split) document-upload slice: the registratie process
now parks at a **`WachtOpDocumenten`** user task with an **interrupting `P30D` boundary timer**. When
the documents arrive the task completes and the process continues into the diploma routing (S-13) →
Beoordelen; if the 30 days lapse, the timer cancels the wait, runs a `RegistratieVerlopen`
external-worker task, and the domain expires the aggregate to a new terminal status **`Verlopen`**.
Backend only — the real upload trigger (portal → BFF → ACL → Documenten API) is S-10b (#103).

Closes #102

Mechanism recorded in **ADR-0017**; opened as proposal #104. Mirrors the S-14 escalation
(boundary-timer + external-worker) and S-11 withdrawal (interrupting cancel) patterns.

## Definition of Done

- [x] Linked Gitea issue (above).
- [x] Failing test committed before the implementation (red→green pairs per layer).
- [x] Implementation makes the test pass.
- [x] Conventional Commits referencing the issue (`refs #102`).
- [ ] CI green — all Gitea Actions jobs (pending on this PR).
- [x] `docker compose up` health unaffected (no new services; deploy path unchanged).
- [x] Docs updated (ADR-0017, demo-script, BACKLOG split).
- [x] ADR added (`docs/architecture/adr-0017-document-wait-timeout-cancellation.md`).
- [x] Demo note in `docs/demo-script.md`.

## Notes for reviewers

- **Domain** (`Registration.Expire()` + `Verlopen`), **application** (`ExpireRegistrationWorker`),
  **infra** (`RegistratieVerlopenProcessor`/`Pump`, `IRegistratieVerlopenClient`, Flowable
  acquire/complete + `CompleteDocumentWaitAsync`) — the timeout counterpart to the OpenZaak/escalation
  worker trios; idempotent per §8.6.
- **BPMN** verified live against a `flowable-rest` probe: complete `WachtOpDocumenten` → routes to
  Beoordelen; fire the P30D timer → `RegistratieVerlopen` job (carrying `registrationId`) + the wait
  task cancelled. `verify-domain` exercises both branches in-stack (completes the wait in every existing
  block; fires the timer and asserts `Verlopen` in a new block).
- **Scope boundary:** on expiry the aggregate goes `Verlopen` and the process ends, but the ZGW *zaak*
  is not yet set to a cancellation status — that needs a new ACL method + statustype seeding and is
  folded into S-10b (noted in ADR-0017).
- `CompleteDocumentWaitAsync` is built and HTTP-tested here but not yet called from a domain endpoint;
  S-10b wires the upload trigger to it.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Reviewed-on: #105

tests/acceptance/Support/InMemoryDomainPorts.cs

@@ -14,6 +14,7 @@ public sealed class InMemoryWorkflowClient : IWorkflowClient
     public RegistrationId? StartedFor { get; private set; }
     public DiplomaOrigin? StartedWithOrigin { get; private set; }
     public string? WithdrawnProcessInstanceId { get; private set; }
+    public string? CompletedDocumentWaitFor { get; private set; }
 
     public Task<string> StartRegistrationProcessAsync(
         RegistrationId registrationId, DiplomaOrigin diplomaOrigin, CancellationToken ct = default)
@@ -28,6 +29,12 @@ public sealed class InMemoryWorkflowClient : IWorkflowClient
         WithdrawnProcessInstanceId = processInstanceId;
         return Task.CompletedTask;
     }
+
+    public Task CompleteDocumentWaitAsync(string processInstanceId, CancellationToken ct = default)
+    {
+        CompletedDocumentWaitFor = processInstanceId;
+        return Task.CompletedTask;
+    }
 }
 
 /// <summary>An in-memory ACL stand-in: records the bsn it opened a zaak for and returns a fixed URL,
@@ -130,6 +137,57 @@ public sealed class InMemoryEscalatieClient : IBeoordelingEscalatieClient
     }
 }
 
+/// <summary>An in-memory Flowable stand-in for the document-timeout scenario (S-10a): it models one
+/// WachtOpDocumenten wait per process instance — whether it is still open and the registration it
+/// correlates to — and the RegistratieVerlopen jobs the interrupting 30-day boundary timer parks. It
+/// drives the timeout worker's behaviour without a running Flowable; the timer firing live is the
+/// verify-domain check.</summary>
+public sealed class InMemoryDocumentTimeoutClient : IRegistratieVerlopenClient
+{
+    private sealed class Wait
+    {
+        public required RegistrationId RegistrationId { get; init; }
+        public bool IsWaiting { get; set; } = true;
+    }
+
+    private readonly Dictionary<string, Wait> _waits = [];
+    private readonly List<RegistratieVerlopenJob> _parked = [];
+    private int _seq;
+
+    /// <summary>A registration parks at WachtOpDocumenten, waiting for the citizen's documents.</summary>
+    public string ParkWaitingForDocuments(RegistrationId registrationId)
+    {
+        var pid = $"pi-{++_seq}";
+        _waits[pid] = new Wait { RegistrationId = registrationId };
+        return pid;
+    }
+
+    /// <summary>The documents arrive before the timer fires: the wait task closes, so the interrupting
+    /// timer no longer fires (mirrors the Workflow Client completing WachtOpDocumenten).</summary>
+    public void ReceiveDocuments(string processInstanceId) => _waits[processInstanceId].IsWaiting = false;
+
+    /// <summary>The 30-day interrupting boundary timer fires: if still waiting, it cancels the wait and
+    /// parks a RegistratieVerlopen job carrying the correlated registration id. A no-op if the documents
+    /// already arrived (the wait/timer race, §8.6).</summary>
+    public void FireDocumentTimer(string processInstanceId)
+    {
+        var wait = _waits[processInstanceId];
+        if (!wait.IsWaiting)
+            return;
+        wait.IsWaiting = false;
+        _parked.Add(new RegistratieVerlopenJob($"job-{++_seq}", wait.RegistrationId));
+    }
+
+    public Task<IReadOnlyList<RegistratieVerlopenJob>> AcquireRegistratieVerlopenJobsAsync(int maxJobs, CancellationToken ct = default)
+        => Task.FromResult<IReadOnlyList<RegistratieVerlopenJob>>(_parked.Take(maxJobs).ToList());
+
+    public Task CompleteRegistratieVerlopenJobAsync(string jobId, CancellationToken ct = default)
+    {
+        _parked.RemoveAll(j => j.JobId == jobId);
+        return Task.CompletedTask;
+    }
+}
+
 /// <summary>An in-memory registration store for the domain acceptance scenario.</summary>
 public sealed class InMemoryRegistrationStore : IRegistrationStore
 {