Bar's secondary line is now a horizontal cluster of the same six
pills used in the page header, followed by the viewed stage label.
Active pill expands and gains a slow halo (rail-pulse keyframe) when
in the bar; same component runs without the pulse in the static
header. Width transitions smoothly between ranks as the user scrolls,
so the indicator visibly tracks progress through the form.
StageProgress now takes an optional `pulse` prop and tightens its
transition timing for nicer scroll-driven animation.
Joel Brock
de53fde1f7