The mobile bottom bar now draws a single absolutely positioned grape pill
(top 10 px, height 42 px) behind its items and implements handoff Motion
section 1: on a tab change it slides the pill from the old item's left and
width to the new one's over 420 ms on the --ease-spring curve, FLIPs every
moved item with the same timing, and fades the new label in (220 ms
ease-out after 120 ms). Icon colour crossfades via transition color .2s.
Under prefers-reduced-motion the pill jumps with no animation. The pill is
re-placed on resize and once document.fonts.ready resolves. Each item
keeps the full 62 px bar height as its tap target.
Maestro task d340ae00-3c2a-48cf-9ac6-35e0b8ed5a7c
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>