Centered card with navbar, lock icon, sans-serif stack (error pages
previously rendered in the browser default serif), and action-aware
copy: permission denial offers only 'Back to Tools' instead of a
pointless 'Try again'; auth failures keep Try again + Back to Tools.
Two-column editor at >=900px (crop pad + cleaned preview left, cleaning/
review controls right), single column below; panel headers wrap their
hints onto their own line on narrow screens.