core: Mouse position is incorrect when system scale isn't 100%

[msg-programs]

On Windows 10, the mouse position is scaled by the value set under system scale under Settings > System > Scale and Layout relative to the top left corner of the window.

There's an issue about this problem on the Pixi repo since that's where I encountered the bug a while back. After some discussion with foxnne on discord they came to the conclusion that it's likely a Mach issue, but I never got around to actually opening an issue here until now.