tmux: Bind MouseDragEnd1StatusDefault w/o run-shell

The special token `$` indicates the highest-numbered window. Also switch
to using before `^` when moving to the front for consistency.

.config/tmux/tmux.conf

@@ -169,14 +169,15 @@ bind -r P swap-window -d -t :-1
 # Reorder windows by dragging them in the status line.
 bind -n MouseDrag1Status swap-window -d -t=
 
+# Move a window to the first or very last position
 # TODO: do nothing on drags that don't start on a window name
 # NOTE: mouse_{x,y} were not set in status line before 3.3
 if -F "#{>=:#{version},3.3}" {
 	bind -n MouseDragEnd1StatusDefault {
 		if -F "#{e|>|f|0:#{mouse_x},#{e|/|f:#{window_width},2}}" {
-			run-shell "tmux move-window -at #{last_window_index}"
+			move-window -at :$
 		} {
-			move-window -t0
+			move-window -bt :^
 		}
 	}
 }