The admin sets the html font size to 14px, so the rem utilities w-11 and
size-5 shrank the track to 38.5px and the knob to 17.5px against the
fixed 26px height and 18px travel. Use w-[44px] and size-[20px] so the
knob sits in a symmetric 3px inset at both ends. Rebuild the embedded
admin shell.