feat: route bounded hierarchy postbox copies

tests/test_router.py

@@ -297,6 +297,23 @@ class PostboxRouterTests(unittest.TestCase):
         self.assertEqual(200, unread.status_code, unread.text)
         self.assertEqual(0, unread.json()["total"])
 
+    def test_routing_dry_run_explains_default_disabled_state(self) -> None:
+        response = self.client.post(
+            "/api/v1/postbox/routing/dry-run",
+            json={
+                "target": {"postbox_id": self.postbox_id},
+                "producer_module": "campaigns",
+                "classification": "internal",
+            },
+        )
+
+        self.assertEqual(200, response.status_code, response.text)
+        self.assertEqual("disabled", response.json()["status"])
+        self.assertEqual(
+            ["hierarchy_routing_disabled"],
+            response.json()["diagnostics"],
+        )
+
 
 if __name__ == "__main__":
     unittest.main()