Replaces the plain bottom SnackBar with a BoosterHint pill that floats in
the empty space above the board: season-accent coloured, a breathing glow
that pulses only while armed (idle otherwise — no wasted ticker), slides/
fades in, shows the booster icon + prompt, and cancels on tap. 3 widget
tests; full suite 234 green.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
