[autocomplete] `disabled` item can be highlighted

# Bug report

## Current behavior

A `disabled` Autocomplete Item can be focused/highlighted using keyboard and pointer events and ends up with the `data-highlighted` attribute.
```jsx

Test

```

## Expected behavior

The disabled items should not be interactive and shouldn't have `data-highlighted` attribute.

## Reproducible example

https://stackblitz.com/edit/2fydq8ct?file=src%2FApp.tsx

## Base UI version

v1.4.1

## Which browser are you using?

Chrome

## Which OS are you using?

Mac OS

## Which assistive tech are you using (if applicable)?

Not applicable

## Additional context

None