test: generated nav manifest guards the sidebar truth

test/nav_manifest_test.dart derives docs/nav.generated.json from
the _pages list (order = Cmd numbers), the labelOf switch, and both
.arb files. On any nav change it regenerates the manifest and fails
once with instructions to commit + mirror it to
fai_chain/docs/studio/, where the platform repo's docs_consistency
gate checks the operator guide against it — cross-repo nav drift
becomes a red gate instead of quietly rotting docs.

Signed-off-by: flemming-it <stefan.a.flemming@googlemail.com>

docs/nav.generated.json

@@ -0,0 +1,53 @@
+{
+  "_generated": "by test/nav_manifest_test.dart — do not edit. Mirror to fai_chain/docs/studio/nav.generated.json (same content).",
+  "pages": [
+    {
+      "id": "welcome",
+      "cmd": 1,
+      "label_de": "Willkommen",
+      "label_en": "Welcome"
+    },
+    {
+      "id": "store",
+      "cmd": 2,
+      "label_de": "Store",
+      "label_en": "Store"
+    },
+    {
+      "id": "doctor",
+      "cmd": 3,
+      "label_de": "Diagnose",
+      "label_en": "Doctor"
+    },
+    {
+      "id": "flows",
+      "cmd": 4,
+      "label_de": "Flows",
+      "label_en": "Flows"
+    },
+    {
+      "id": "audit",
+      "cmd": 5,
+      "label_de": "Protokoll",
+      "label_en": "Audit"
+    },
+    {
+      "id": "approvals",
+      "cmd": 6,
+      "label_de": "Freigaben",
+      "label_en": "Approvals"
+    },
+    {
+      "id": "runs",
+      "cmd": 7,
+      "label_de": "Läufe",
+      "label_en": "Runs"
+    },
+    {
+      "id": "federation",
+      "cmd": 8,
+      "label_de": "Föderation",
+      "label_en": "Federation"
+    }
+  ]
+}