Locomotion: a stop from a run slides the planted toe 118 mm (no stop played by distance) #828

The case. A figure on ae3d.locomotion with legs on ae3d.feet, stopping from a run, slides its planted toe 118 mm in one plant: locomotion.go_to running to a spot 10 m ahead, braking at 3 m/s² to stop on it (#825 item 1). Walking, the same stop slides 4.3 mm.

Why, as far as measured. Braking from the run's speed crosses the run clip, the walk clip and the idle, inertialized from one to the next (figure.play_blended). Each clip is paced to the body's speed, but through a blend the drawn feet are a mix of two cycles' feet, and the hold (#611) keeps only the lowest of them. Nothing plays a stop.

What shipped games do: Distance Matching (Paragon, GDC 2016; Unreal's distance matching node). A stop clip is played by the distance left to the stop point, not by time, so its feet plant where the clip planted them and the body ends on the mark. Motion matching with stop clips in its database gets the same.

For ae3d: where the figure has a stop clip, play it by distance to the spot go_to is stopping on. Where it has none, the stop's last steps can be planned on the feet, as #827 proposes for turns. Measured by toe slide per plant (5 mm), as #825 asks.

Part of #825; related to #509 and #611.