Fixes pathfinding not checking diagonal passability properly. (#65665)

In short, it was checking diagonal passability directly instead of every partial-step.
Now this obviously makes this pricier.
Partially alleviates the secbot pathing doomstack stacks since they will now properly fail to path but i still need to find the breakpoint where the image churn causes the actual client crash.
Also removes redundant path calculation in bot code that would be overwritten on step anyway.

code/__HELPERS/path.dm

@@ -44,7 +44,7 @@
  * Note that this can only be used inside the [datum/pathfind][pathfind datum] since it uses variables from said datum.
  * If you really want to optimize things, optimize this, cuz this gets called a lot.
  */
-#define CAN_STEP(cur_turf, next) (next && !next.density && cur_turf.Adjacent(next) && !(simulated_only && SSpathfinder.space_type_cache[next.type]) && !cur_turf.LinkBlockedWithAccess(next,caller, id) && (next != avoid))
+#define CAN_STEP(cur_turf, next) (next && !next.density && !(simulated_only && SSpathfinder.space_type_cache[next.type]) && !cur_turf.LinkBlockedWithAccess(next,caller, id) && (next != avoid))
 /// Another helper macro for JPS, for telling when a node has forced neighbors that need expanding
 #define STEP_NOT_HERE_BUT_THERE(cur_turf, dirA, dirB) ((!CAN_STEP(cur_turf, get_step(cur_turf, dirA)) && CAN_STEP(cur_turf, get_step(cur_turf, dirB))))
 
@@ -338,8 +338,21 @@
  * * simulated_only: Do we only worry about turfs with simulated atmos, most notably things that aren't space?
 */
 /turf/proc/LinkBlockedWithAccess(turf/destination_turf, caller, ID)
+	if(destination_turf.x != x && destination_turf.y != y) //diagonal
+		var/in_dir = get_dir(destination_turf,src) // eg. northwest (1+8) = 9 (00001001)
+		var/first_step_direction_a = in_dir & 3      // eg. north   (1+8)&3 (0000 0011) = 1 (0000 0001)
+		var/first_step_direction_b = in_dir & 12  // eg. west   (1+8)&12 (0000 1100) = 8 (0000 1000)
+
+		for(var/first_step_direction in list(first_step_direction_a,first_step_direction_b))
+			var/turf/midstep_turf = get_step(destination_turf,first_step_direction)
+			var/way_blocked = LinkBlockedWithAccess(midstep_turf,caller,ID) || midstep_turf.LinkBlockedWithAccess(destination_turf,caller,ID)
+			if(!way_blocked)
+				return FALSE
+		return TRUE
+
 	var/actual_dir = get_dir(src, destination_turf)
 
+	// Source border object checks
 	for(var/obj/structure/window/iter_window in src)
 		if(!iter_window.CanAStarPass(ID, actual_dir))
 			return TRUE
@@ -352,6 +365,11 @@
 		if(!iter_rail.CanAStarPass(ID, actual_dir))
 			return TRUE
 
+	for(var/obj/machinery/door/firedoor/border_only/firedoor in src)
+		if(!firedoor.CanAStarPass(ID, actual_dir))
+			return TRUE
+
+	// Destination blockers check
 	var/reverse_dir = get_dir(destination_turf, src)
 	for(var/obj/iter_object in destination_turf)
 		if(!iter_object.CanAStarPass(ID, reverse_dir, caller))

code/game/machinery/doors/firedoor.dm

@@ -581,6 +581,9 @@
 	if(!(border_dir == dir)) //Make sure looking at appropriate border
 		return TRUE
 
+/obj/machinery/door/firedoor/border_only/CanAStarPass(obj/item/card/id/ID, to_dir)
+	return !density || (dir != to_dir)
+
 /obj/machinery/door/firedoor/border_only/proc/on_exit(datum/source, atom/movable/leaving, direction)
 	SIGNAL_HANDLER
 	if(leaving.movement_type & PHASING)

code/modules/mob/living/simple_animal/bot/bot.dm

@@ -318,7 +318,7 @@
 			call_mode()
 			return FALSE
 		if(BOT_SUMMON) //Called to a location
-			bot_summon()
+			summon_step()
 			return FALSE
 	return TRUE //Successful completion. Used to prevent child process() continuing if this one is ended early.
 
@@ -785,8 +785,6 @@ Pass a positive integer as an argument to override a bot's default speed.
 			mode = BOT_SUMMON
 			speak("Responding.", radio_channel)
 
-			calc_summon_path()
-
 		if("ejectpai")
 			ejectpairemote(user)
 	return
@@ -813,9 +811,6 @@ Pass a positive integer as an argument to override a bot's default speed.
 		else
 			to_chat(src, span_warning("Unidentified control sequence received:[command]"))
 
-/mob/living/simple_animal/bot/proc/bot_summon() // summoned to PDA
-	summon_step()
-
 // calculates a path to the current destination
 // given an optional turf to avoid
 /mob/living/simple_animal/bot/proc/calc_path(turf/avoid)