Play, Pause and Stop animation take the animation on a port instead of a
fixed setting, fed by the new Animation literal or a list item tagged
`$animation`. Playing an animation already running keeps its frame but
counts it as started last, so turning back to a walk that never stopped
shows that walk. The actor demo walks through one Play animation over
`ItemAt(walk, facing)` again and stops every animation to stand.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>