fix: Advanced section layout - prevent horizontal overflow

Change path fields from single-row (label+input+buttons) to two-row layout:
label with status dot on top, input field + browse/clear buttons below.
TextField uses flexGrow=1 + flexShrink=1 + minWidth=0 to properly shrink.
Buttons use flexShrink=0 to keep fixed width.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>