This PR fixes an issue where mouse selection in the terminal would be
offset when the Terminal Inline Assistant was active. The problem was
caused by incorrect coordinate translation when handling mouse events
with an active inline assistant.

The fix adjusts mouse event coordinates by properly accounting for the
terminal view's `scroll_top` value when the inline assistant is present,
ensuring that text selection precisely follows the mouse cursor
position.

Closes #26111 

Release Notes:

- Fixed text selection misalignment in terminal when the inline
assistant is active

Co-authored-by: Peter Tripp <peter@zed.dev>