bug(Button toggle): Voice Over not read status pressed / not pressed after select and deselect

### Is this a regression?

- No.

### Description

Voice Over does not read the state of the button as pressed when selected or not pressed when deselected. It only reads 'selected' if you change focus and return to the selected button. The NVDA screen reader does not have this problem, it reads the states correctly.

### Reproduction

Steps to reproduce:
1. Go to official multiple selection example: https://material.angular.io/components/button-toggle/examples#button-toggle-mode
2. Focus those buttons with VO open
3. States presses/ not pressed not announced when toggle buttons

### Expected Behavior

VO should read pressed/ not pressed when button toggled like NVDA do this.

### Actual Behavior

Voice Over does not read the state of the button as pressed when selected or not pressed when deselected.

### Environment

- Angular: 19.2.7
- CDK/Material: 19.2.10
- Browser(s): Chrome, Edge, FF, Safari
- Operating System (e.g. Windows, macOS, Ubuntu): MacOS 15.4.1

https://material.angular.io/components/button-toggle/examples#button-toggle-mode にある公式の複数選択 button-toggle の例から始め、VoiceOver で問題を再現してから、NVDA での動作と比較します。toggle の選択と選択解除によって、フォーカスを移動せずに VoiceOver が押下状態と非押下状態を読み上げるようになれば、変更は完了です。

索引モデルが issue の本文から書いたものです。