Window close delayed when in `UpdateMode::Reactive`

## Bevy version

main branch

## What you did

I clicked the "close" button for a window and didn't move my mouse while using `UpdateMode::Reactive`.

## What went wrong

I expected the window to close immediately; the window waited until the next scheduled update to close.

## Additional information

When using `UpdateMode::Reactive`, the application updates when new user event are generated, or the wait time has run out. By not moving my mouse, no additional user events were generated and the window waited for the wait time to run out before closing.

Start by tracing UpdateMode::Reactive scheduling together with the window close event handling, then reproduce the issue without moving the mouse. Done means a close request causes the window to close immediately rather than waiting for the next scheduled update.

Written by the indexing model from the issue text.