Removes the DropdownPanel component that depended on the external `glass`
CSS class. Uses inline {open && <div bg-[#111]>} pattern and a single
dropdownRef, consistent with ImageStudio.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
overflow-x-auto implicitly sets overflow-y:auto, creating a clipping
context that cut off the upward-opening position:absolute dropdown
panels. Changed to flex-wrap so buttons wrap on narrow screens and
dropdowns display correctly.