Instant full-speed-on-press / dead-stop-on-release was the jerky/jarring feel
and made the anim pop Idle->Run. Now MoveTowards-ramps horizontal velocity
(accel 45, decel 60 m/s^2), so starts/stops ease and Idle->Walk->Run blends.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>