fixes can_see not working (#86517)

## About The Pull Request
can_see wasnt working after the new inbuilt byond procs were introduced
to it.

## Why It's Good For The Game
closes #86515

## Changelog
🆑
fix: basic mobs will now act hostile again
/🆑

---------

Co-authored-by: Ghom <42542238+Ghommie@users.noreply.github.com>

code/__HELPERS/atoms.dm

@@ -63,9 +63,9 @@
 	var/turf/target_turf = get_turf(target)
 	if(get_dist(source, target) > length)
 		return FALSE
-	if(current == target_turf)//they are on the same turf, source can see the target
+	if(current == target_turf || source.CanReach(target))//they are on the same turf or in reach, source can see the target
 		return TRUE
-	var/list/steps = get_steps_to(current, target_turf)
+	var/list/steps = get_steps_to(source, target)
 	if(isnull(steps) || length(steps) > length)
 		return FALSE
 	for(var/direction in steps)

code/modules/unit_tests/_unit_tests.dm

@@ -107,6 +107,7 @@
 #include "breath.dm"
 #include "burning.dm"
 #include "cable_powernets.dm"
+#include "can_see.dm"
 #include "card_mismatch.dm"
 #include "cardboard_cutouts.dm"
 #include "cargo_dep_order_locations.dm"

code/modules/unit_tests/can_see.dm

@@ -0,0 +1,7 @@
+/// Unit test to make sure can_see is working properly
+/datum/unit_test/can_see_test
+
+/datum/unit_test/can_see_test/Run()
+	var/mob/living/carbon/human/observer = allocate(/mob/living/carbon/human/consistent, run_loc_floor_bottom_left) //make sure they're both apart
+	var/mob/living/carbon/human/to_be_seen = allocate(/mob/living/carbon/human/consistent, run_loc_floor_top_right)
+	TEST_ASSERT(can_see(observer, to_be_seen, get_dist(observer, to_be_seen)), "can_see returned false despite dummies being able to see one another!")