bug(mat-menu): VoiceOver user on mobile is able to navigate out of an opened Menu

### Description

On iOS, with VoiceOver turned on, after a user opens a menu and they start swiping through the menu items in order to move focus from one item to the next, when they reach the first or last menu item and swipe respectively backward or forward, VoiceOver focus is moved outside of the menu into the next element

### Reproduction

StackBlitz link: https://material.angular.dev/components/menu/overview#menu-overview
Steps to reproduce:
1. On an iOS device, turn VoiceOver on
2. Navigate to the menu example
3. Open the menu
4. Swipe forward until VoiceOver focus leaves the menu

### Expected Behavior

Focus is trapped in the menu

### Actual Behavior

VoiceOver focus moves outside of the menu

### Environment

- Angular: v21
- CDK/Material: v21
- Browser(s): Any
- Operating System (e.g. Windows, macOS, Ubuntu): iOS with VoiceOver turned on

首先，在启用 VoiceOver 的 iOS 设备上复现链接的 Material 菜单概览中的问题，然后跟踪第一个和最后一个菜单项处的 mat-menu 焦点处理。完成的标准是，向前和向后滑动时，VoiceOver 焦点会保持在已打开的菜单内，而不是移动到下一个元素。

由索引模型根据 Issue 内容生成。