bug(mat-chip-grid): impossible to navigate to the input using VoiceOver commands when there are chips selected

### Is this a regression?

- [ ] Yes, this behavior used to work in the previous version

### The previous version in which this bug was not present was

_No response_

### Description

When nesting input inside of the mat-chip-grid, it becomes inaccessible with the screenreader commands (when there are chips selected).

### Reproduction

StackBlitz link: https://stackblitz.com/run?file=src%2Fexample%2Fchips-input-example.html
Steps to reproduce:
1. Use material chips with input, where input is nested inside of mat-chip-grid.
2. Add at least one chip.
3. Start VoiceOver and focus the form field.
4. Navigate inside the form field using VoiceOver commands (e.g. VO-Right Arrow to move to the next item)

### Expected Behavior

It should be possible to focus the input element when pressing VO-Right Arrow inside the mat-chip-grid. Similar to how it is in chip-autocomplete example, when input is not inside the mat-chip-grid:
https://stackblitz.com/run?file=src%2Fexample%2Fchips-autocomplete-example.css

### Actual Behavior

Only chips and delete buttons can be focused using VoiceOver commands.

### Environment

- Angular: 19.0.5
- CDK/Material: 19.0.5
- Browser(s): Chrome
- Operating System (e.g. Windows, macOS, Ubuntu): MacOS

Bắt đầu bằng cách tái hiện sự cố trong ví dụ StackBlitz được liên kết với Angular Material 19.0.5 trên macOS và VoiceOver, làm theo các bước được liệt kê sau khi thêm một chip. Đọc các ví dụ mat-chip-grid và chip-autocomplete để so sánh hành vi của focus; hoàn tất khi VO-Right Arrow có thể tiếp cận input lồng nhau trong khi các chip vẫn được chọn.

Do mô hình lập chỉ mục viết ra từ nội dung của issue.