fix(import): remove resourceName/executionRoleArn co-variance refine (#996)

The refine required both fields to be set together, but resourceName
is always needed on import (to preserve the AWS name) while
executionRoleArn is only present when the gateway has a custom role.
Gateways without a custom role (service auto-creates one) fail the
refine because resourceName is set but executionRoleArn is not.

Keep the individual field validations (GatewayNameSchema for
resourceName, regex for executionRoleArn).

Author: jesseturner21

src/schema/schemas/mcp.ts

@@ -615,11 +615,7 @@ export const AgentCoreGatewaySchema = z
       message: 'customJwtAuthorizer configuration is required when authorizerType is CUSTOM_JWT',
       path: ['authorizerConfiguration'],
     }
-  )
-  .refine(data => (data.resourceName !== undefined) === (data.executionRoleArn !== undefined), {
-    message: 'resourceName and executionRoleArn must be set together (import) or both omitted (fresh gateway)',
-    path: ['resourceName'],
-  });
+  );
 
 export type AgentCoreGateway = z.infer<typeof AgentCoreGatewaySchema>;