Address review feedback: zod import path and legacy route ref

Use explicit zod/v4 import path in tests, and remove unnecessary
convertLegacyRouteRef wrapper in catalog-graph README.

Signed-off-by: Patrik Oldsberg <poldsberg@gmail.com>
Made-with: Cursor

packages/frontend-plugin-api/src/schema/createPortableSchema.test.ts

@@ -14,7 +14,7 @@
  * limitations under the License.
  */
 
-import { z as zodV4 } from 'zod';
+import { z as zodV4 } from 'zod/v4';
 import {
   createConfigSchema,
   mergePortableSchemas,