Fix iframe selector in savePreference to target portal iframe

The unqualified 'iframe' selector matches both the app's portal iframe
and the Charlotte AI iframe, causing a strict mode violation. Use
'iframe[name="portal"]' to match the parent class pattern.

Author: mraible

e2e/src/pages/UserPreferencesExtensionPage.ts

@@ -23,7 +23,7 @@ export class UserPreferencesExtensionPage extends HostPanelExtensionPage {
   async savePreference(): Promise<void> {
     return this.withTiming(
       async () => {
-        const iframe = this.page.frameLocator('iframe');
+        const iframe = this.page.frameLocator('iframe[name="portal"]');
 
         // Wait for Save button to confirm form is loaded
         await expect(iframe.getByRole('button', { name: /Save Preferences/i })).toBeVisible({ timeout: 10000 });