test(design): add the starter-roles endpoint to the URL enumeration

CI caught it: tests/test_routes_design_systems.py enumerates every routed rule,
and I added a handler without adding its rule. The guard doing exactly what its
docstring says it is for.

Two enumerations govern this blueprint and I had only extended one — the
parity list (handlers exist on both surfaces) but not the URL list (handlers
are actually routed). They catch different failures, which is why both exist.

Noted in place: /api/design-systems/starter-roles is a static segment sharing a
prefix with /api/design-systems/<int:design_system_id>. That pairing is where a
silently-shadowed route hides, so it is worth being explicit that the int
converter cannot match "starter-roles" — verified rather than assumed.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01UaYUaouG9jjhATyuxCKrQs

tests/test_routes_design_systems.py

@@ -44,6 +44,11 @@ def test_every_endpoint_is_reachable_on_the_app():
     }
     assert rules == {
         "/api/design-systems",
+        # Static segment, declared before the <int:...> rule reads it — Quart's
+        # int converter will not match "starter-roles", so the two cannot
+        # collide. Worth stating: a static-vs-dynamic sibling on the same prefix
+        # is exactly where a silently-shadowed route hides.
+        "/api/design-systems/starter-roles",
         "/api/design-systems/<int:design_system_id>",
         "/api/design-systems/<int:design_system_id>/resolved",
         "/api/design-systems/<int:design_system_id>/stylesheet",