[UI] Tab attachability UI indicator goes out of bounds above screen when maximized

### Description of the new feature


Minor UI improvement: When dragging a tab into a terminal window, if the window is maximized, the “attachability” indicator is not visible. This is exacerbated by the fact that the valid attachment area is small. While this is a minor inconvenience, it seems like it should be a relatively minor fix as well.

Thanks!

### Proposed technical implementation details

_No response_