Leave the last vehicle's coupler at 0 so the train gets its end signals

The simulator hangs end signals only on a last vehicle with coupler 0; every
new car came with 3 and the pass that couples neighbours never touched the
last one, nor did taking a car off the end. The coupler editor says so for
the last vehicle.

StarterNG/Views/Depot/VehicleDetails.cs

@@ -179,6 +179,8 @@ public sealed class VehicleDetails
             return;
 
         bool isLast = unitIdx >= _consist.Count - 1;
+        if (isLast)
+            couplerPanel.Children.Add(PanelNote(App.Loc["CouplingLastNote"]));
 
         var d = Consist.TailCar(item);