A boat stops when its rider gets out

AbstractBoat.tick drops a boat's cached motion on the side that does not drive
it, so the level takes a boat over at a standstill when its rider leaves.
Horizon kept the velocity of the ride, and the empty boat went on gliding.

crates/horizon-client/src/game/boats.rs

@@ -1047,6 +1047,13 @@ impl Game<'_> {
     /// floor there, else on top of the boat.
     pub(super) fn dismount(&mut self, i: usize) {
         self.riding = None;
+        // `AbstractBoat.tick`'s non-authoritative branch: the copy of a boat
+        // that no player of this side drives drops its cached motion
+        // (`setDeltaMovement(Vec3.ZERO)`, `deltaRotation = 0`) and is not
+        // moved, so a boat is at a standstill when its rider gets out instead
+        // of coasting on the velocity of the ride that just ended.
+        self.boats[i].velocity = Vec3::ZERO;
+        self.boats[i].delta_rotation = 0.0;
         let target = self.boat_dismount_target(i, 0.6, self.yaw);
         if let Some(p) = self.player.as_mut() {
             p.position = target;