The dialog's mousedown listener was attached to the whole root and
unconditionally called preventDefault(), which blocked the target
element from receiving focus. As a result, the custom target <input>
and the milestone <select> could never be focused.
Only initiate drag (and only preventDefault) when the mousedown is on
the .tat-header bar. This lets the user click into inputs, selects, and
buttons inside the dialog body, while still allowing the dialog to be
dragged from the title bar.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
