fix(workflow): use a DMN service task, not businessRuleTask (S-13, refs #14)

flowable-rest's businessRuleTask parse handler binds the legacy Drools/KIE
implementation (NoClassDefFoundError: org.kie.api...AgendaFilter at deploy time),
so registratie.bpmn failed to deploy and flowable-init exited 22. Flowable's
supported inline-DMN construct is a serviceTask with flowable:type="dmn" — switch
to it. The DMN cross-deploy via the process repository (previous commit) was fine;
this was the BPMN parse. Docs/comments updated to match.

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

docs/architecture/adr-0016-diploma-eligibility-dmn.md

@@ -1,4 +1,4 @@
-# ADR-0016: Diploma eligibility is a DMN evaluated inline as a BPMN businessRuleTask
+# ADR-0016: Diploma eligibility is a DMN evaluated inline as a BPMN DMN service task
 
 - **Status:** Accepted
 - **Date:** 2026-07-17
@@ -22,14 +22,16 @@ back. That is one option; it is not the only one, and it is not the cleanest.
 ## Decision
 
 **The diploma-eligibility DMN is deployed to Flowable and evaluated inline by the registratie process
-as a `businessRuleTask`; an exclusive gateway routes on its output. The domain's only new job is to
-carry the diploma origin and pass it into the process as a start variable.**
+as a DMN service task (`flowable:type="dmn"`); an exclusive gateway routes on its output. The domain's
+only new job is to carry the diploma origin and pass it into the process as a start variable.**
 
 - **The decision lives in the workflow.** `workflows/diploma-eligibility.dmn` maps `diplomaOrigin`
-  → `route` (`Buitenlands` ⇒ `CBGV_ADVIES`, otherwise `DIRECT`). A `businessRuleTask`
+  → `route` (`Buitenlands` ⇒ `CBGV_ADVIES`, otherwise `DIRECT`). A DMN service task
   (`flowable:type="dmn"`, `decisionTableReferenceKey=diploma-eligibility`) runs it between
   `OpenZaakAanmaken` and `Beoordelen`, and an exclusive gateway sends `CBGV_ADVIES` through a new
-  `CBGVAdvies` user task before `Beoordelen`, `DIRECT` straight there.
+  `CBGVAdvies` user task before `Beoordelen`, `DIRECT` straight there. (A `businessRuleTask` would
+  bind Flowable's legacy Drools/KIE implementation, which `flowable-rest` does not bundle — its parse
+  handler throws `NoClassDefFoundError` at deploy time; the DMN service task is the supported route.)
 - **The domain carries the input, not the decision.** The `Registration` aggregate gains a
   `DiplomaOrigin` (Binnenlands/Buitenlands); `SubmitRegistration` passes it to
   `StartRegistrationProcessAsync`, which sets it as the `diplomaOrigin` start variable. The domain
@@ -52,7 +54,7 @@ carry the diploma origin and pass it into the process as a start variable.**
 
 - Deviates from #14's literal "evaluated by the Domain Service via Workflow Client" wording (noted on
   the issue). The outcome — DMN decides eligibility, foreign diplomas get the CBGV step — is unchanged.
-- The DMN and its `businessRuleTask` wiring are validated live (verify-domain drives a foreign
+- The DMN and its service-task wiring are validated live (verify-domain drives a foreign
   registration through CBGV-advies and a domestic one straight to beoordeling, exercising both
   branches), not in unit tests — consistent with ADR-0009/0014/0015. The domain unit/acceptance tests
   cover only that the origin is carried into the process.

docs/demo-script.md

@@ -346,7 +346,7 @@ candidate group behandelaar → teamlead (§8.2).
 
 ## S-13 — Diploma-eligibility: foreign diplomas route through CBGV-advies (#14, ADR-0016)
 
-A registration's diploma origin decides its route. A DMN `businessRuleTask` in the registratie
+A registration's diploma origin decides its route. A DMN service task in the registratie
 process evaluates the `diploma-eligibility` decision on the `diplomaOrigin` start variable: a
 **foreign** (Buitenlands) diploma is routed through an extra **CBGV-advies** user task before
 beoordeling; a **domestic** (Binnenlands) one goes straight to beoordeling. The decision lives in the
@@ -376,7 +376,7 @@ curl -s -u rest-admin:test -X POST "$FL/runtime/tasks/$TID" \
 ```
 
 **The path:** domain sets the `diplomaOrigin` start variable → registratie process DMN
-`businessRuleTask` sets `route` → exclusive gateway → foreign: `CBGVAdvies` user task → `Beoordelen`;
+DMN service task sets `route` → exclusive gateway → foreign: `CBGVAdvies` user task → `Beoordelen`;
 domestic: `Beoordelen` directly (§8.2, ADR-0016).
 
 > The domestic/foreign paths are covered by the `Een diploma op herkomst routeren` acceptance