feat(k8s): declare the six platform deviations so only new drift fails (refs #168)

Six differences exist by design and are now recorded in DEVIATIONS with the reason
each one was forced, so the check passes on today's tree and fails on tomorrow's
accident: the four `*-init` Django services folded into their web pods (one migrator
per database), and the two bootstrap Jobs compose runs from the host instead.

Verified against both drift classes by hand: bumping OPENZAAK_TAG in compose alone
reports openzaak + oz-celery, and adding a workload to values.yaml alone reports it
by name.

infra/helm/check-drift.py

@@ -31,6 +31,26 @@ CHART = ROOT / "infra/helm/big-reference"
 # filterable without teaching the check what busybox is.
 BUSYBOX = "drift-check-ignored-init-image"
 
+# Differences that Kubernetes forces, not drift (ADR-0033). A name listed here is
+# expected to be on exactly one side; anything else fails.
+DEVIATIONS = {
+    # The four Django services apply their own setup_configuration in the web pod
+    # (`args: [sh, -c, "/setup_configuration.sh && exec /start.sh"]`) rather than in a
+    # separate init Job. Both that script and /start.sh run `manage.py migrate`, and
+    # Kubernetes has no `depends_on: service_completed_successfully` to serialise them,
+    # so the Job and its web pod migrated the same database concurrently.
+    "oz-init": "folded into the openzaak pod",
+    "nrc-init": "folded into the nrc-web pod",
+    "objecttypen-init": "folded into the objecttypen pod",
+    "objecten-init": "folded into the objecten pod",
+    # Compose seeds these from the host — the verify scripts `docker cp` the two
+    # scripts into a running container, and docker-compose.local.yml carries
+    # `local-seed` + `nrc-subscribe` for `make local`. A cluster has no host to seed
+    # from, so both became Jobs in the chart.
+    "seed-zaaktype": "compose seeds the catalogus from the host (infra/openzaak/seed_catalogus.py)",
+    "nrc-subscribe": "compose registers the abonnement from the host (infra/local/register-abonnement.py)",
+}
+
 # Workloads the observability backplane adds. Off by default in both stacks'
 # defaults, so they are rendered on purpose here — otherwise their images drift
 # unwatched.
@@ -70,9 +90,9 @@ def main() -> int:
     compose, chart = compose_services(), chart_workloads()
     problems = []
 
-    for name in sorted(set(compose) - set(chart)):
+    for name in sorted(set(compose) - set(chart) - set(DEVIATIONS)):
         problems.append(f"  {name}: in docker-compose.yml, not in the chart")
-    for name in sorted(set(chart) - set(compose)):
+    for name in sorted(set(chart) - set(compose) - set(DEVIATIONS)):
         problems.append(f"  {name}: in the chart, not in docker-compose.yml")
     for name in sorted(set(compose) & set(chart)):
         if compose[name] != chart[name]:
@@ -87,6 +107,8 @@ def main() -> int:
         return 1
 
     print(f"no drift: {len(chart)} workloads, images identical on both stacks")
+    for name, why in sorted(DEVIATIONS.items()):
+        print(f"  deviation (declared): {name} — {why}")
     return 0