With a Shaper Group or one of its faces selected, a Shaper click within
3 screen pixels of one of the group's original shapes' outlines enters
Construction mode with that shape selected, also where the outline runs
through a merged face. shaper.select takes a tolerance in points
(default 3, at most 1000); hidden and locked shapes are skipped, and a
Shaper Group above the selected one still takes the click.