Writable angle from pivot to points[0]; write rotates every input
about pivot by (target − current) via its Pivotal trait (Vec rotates
position, Pose also rotates orientation). pivot is reactive; pass
mean(points) to rotate about the cluster's own centroid.
Writable angle from
pivottopoints[0]; write rotates every input aboutpivotby (target − current) via itsPivotaltrait (Vec rotates position, Pose also rotates orientation).pivotis reactive; passmean(points)to rotate about the cluster's own centroid.