Compact Auto/Manual render toggle button with sticky header

- Replace ToggleButtons with single Button + on_click for reliable toggling
- Split panel into fixed header + scrollable tabs so Auto button stays visible
- Green=Auto, grey=Manual, Apply button appears only in Manual mode

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: brycewang-stanford