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/controllers/subsystem/SSinput.dm

@@ -22,6 +22,8 @@ SUBSYSTEM_DEF(input)
 	return "P: [length(processing)]"
 
 /datum/controller/subsystem/input/fire(resumed = FALSE)
+	// Sleeps in input handling are bad, because they can stall the entire subsystem indefinitely, breaking most movement. key_loop has SHOULD_NOT_SLEEP(TRUE), which helps, but it doesn't catch everything, so we also waitfor=FALSE here, as using INVOKE_ASYNC here is very unperformant.
+	set waitfor = FALSE
 	var/list/to_cull
 	for(var/client/C in processing)
 		if(processing[C] + AUTO_CULL_TIME < world.time)

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()