The tip preview square in the Blob Brush Tool Options set the Angle by a
drag but had no accessible name, no value and no keyboard control.
Screen readers now get it as the Angle slider with the Angle in degrees
as its value. A click or a drag gives it the keyboard focus, and the
arrow keys, Shift with an arrow, Page Up and Page Down, Home and End
step the Angle within -180 to 180 degrees, as the dialog sliders built
on color_slider_stepped do (crates/ui-egui/src/widgets/color.rs). The
new widgets::stepped_area gives a caller-drawn control that slider's
screen-reader node, focus, keys and focus outline.