constrain simgui window placement #8250
Description
Describe the bug
When showing a rookie through simgui yesterday, the very first thing we did was to make the field widget bigger, which they did by dragging one corner (fine) and then moving the title bar up. But they managed to put the widget titlebar above the limits of the simgui window, where it could not be retrieved. It also covered the simgui menu bar, so there was no way to close the widget that way. I looked around for where simgui puts this location, so I could try to save them, but I couldn't find it. Clicking the "reset" menu item didn't fix it either. They were just hosed.
To Reproduce
Steps to reproduce the behavior:
- move a simgui widget up until the titlebar disappears
Expected behavior
constrain widget location so the title bar is never invisible.
Screenshots
Desktop (please complete the following information):
- OS: e.g. Windows 11
- Project Information: WPILib 2025.3.2