CORE-20124 Since `TB_HITTEST` returns negative numbers for ID for separator menu items [^1], shell menu assumes mouse moved outside of the menu popup, highlighting the menu item for currently open submenu. To fix this behavior, we can detect separators in `CMenuFocusManager::ProcessMouseMove` and negate the ID returned by `TB_HITTEST` to make it a positive number again, so the shell menu wouldn't glitch. [^1]: https://learn.microsoft.com/en-us/windows/win32/controls/tb-hittest