[menu][popover] in-Menu Popover closes unexpectedly after re-hovering

# Bug report

## Current behavior

When integrating a confirmation popover on a menu item (such as a "delete" action), the popover appears and displays correctly when the menu item is clicked. I can interact with buttons within the popover while hovering over it. However, if I focus the initial menu item and then blur (move focus away from it), the popover hides, even if the mouse is still over the popover or I want to interact with it again.

## Expected behavior

The popover should remain open and interactive when the menu item is blurred, until an explicit action (such as clicking outside or pressing a Cancel/Confirm button) closes it.

## Reproducible example

https://codesandbox.io/p/sandbox/relaxed-kare-hj6shz

## Base UI version

1.0.0-beta.4

## Which browser are you using?

Chrome

## Which OS are you using?

Mac OS