AccessKit is slow and buggy when Bevy is in continuous update mode

## Bevy version

0.17 (mainline), but applies to any Bevy version.

## \[Optional\] Relevant system information

MacOS Sequoia 15.5

## What you did

Enabling VoiceOver (in Mac system settings) and then run my Bevy app, attempt to use focusable controls.

## What went wrong

The screen reader becomes very laggy and hard to use. If I change my app to use the winit `desktop_app` configuration, the problem disappears.

I'm guessing that either AccessKit or VoiceOver is unhappy when Bevy uses a lot of CPU.

## Additional information

More detailed information and demonstration of the problem in this discussion: https://github.com/AccessKit/accesskit/discussions/542

The discussion was closed because setting `desktop_app` makes the problem go away, but this is not an adequate solution for most Bevy users.