Prevent sleeps in key handling from blocking SSinput (#26761)

* Prevent sleeps in Move from blocking SSinput

* Switch to watifor = FALSE

* Move SHOULD_NOT_SLEEP

* Whoops, that one's a redefine, too.

code/modules/input/input.dm

@@ -5,6 +5,8 @@
 	return
 
 /datum/proc/key_loop(client/C)
+	// Sleeps in input handling are bad, because they can stall the entire subsystem indefinitely, breaking most movement. The subsystem sets waitfor=FALSE, which works around this, but we'd rather avoid the sleeps in the first place.
+	SHOULD_NOT_SLEEP(TRUE)
 	return
 
 /client/key_loop()