Refactors how targeted changeling stings are handled (#14509)

* cling click refactor

* uses middleClickOverride instead

* remove old click_intercept

* this also doesn't need to exist anymore

* wording

* this is more efficient so we don't have to keep New'ing and qdel'ing the datum

code/datums/click_intercept.dm

@@ -1,10 +1,22 @@
+/**
+ * # Click intercept datum
+ *
+ * Datum which is intended to be stored by a client's `click_intercept` variable.
+ * Used to override normal clicking behavior when clicking on an object.
+ * While active, a mob's `ClickOn` proc will redirect to the `InterceptClickOn()` proc instead.
+ */
 /datum/click_intercept
+	/// A reference to the client which is assigned this click intercept datum.
 	var/client/holder = null
+	/// Any `obj/screen/buttons` the client is meant to receive when assigned this click intercept datum.
 	var/list/obj/screen/buttons = list()
 
 /datum/click_intercept/New(client/C)
 	create_buttons()
-	enter(C)
+	holder = C
+	holder.click_intercept = src
+	holder.show_popup_menus = FALSE
+	holder.screen += buttons
 	return ..()
 
 /datum/click_intercept/Destroy()
@@ -15,17 +27,27 @@
 	QDEL_LIST(buttons)
 	return ..()
 
-/datum/click_intercept/proc/enter(client/C)
-	holder = C
-	holder.click_intercept = src
-	holder.show_popup_menus = FALSE
-	holder.screen += buttons
-
+/**
+ * Called when you want to cancel a client's click intercept and return to normal clicking.
+ */
 /datum/click_intercept/proc/quit()
 	qdel(src)
 
+/**
+ * Base proc, intended to be overriden. Code that adds datum specific buttons to the list of `buttons`, should go here.
+ */
 /datum/click_intercept/proc/create_buttons()
 	return
 
-/datum/click_intercept/proc/InterceptClickOn(user,params,atom/object)
+/**
+ * Called in various mob's `ClickOn` procs, which happens when they click on an object in the world.
+ *
+ * If the mob's `client.click_intercept` variable is set to something other than null, calls the `InterceptClickOn` proc for that click intercept datum. Aka, this proc.
+ *
+ * Arguments:
+ * * user - the mob which just clicked on something.
+ * * params - the `params` arguemnt passed from the `ClickOn` proc.
+ * * object - the atom that was just clicked.
+ */
+/datum/click_intercept/proc/InterceptClickOn(mob/user, params, atom/object)
 	return

code/datums/mind.dm

@@ -939,6 +939,8 @@
 					special_role = null
 					if(changeling)
 						current.remove_changeling_powers()
+						qdel(current.middleClickOverride) // In case the old changeling has a targeted sting prepared (`datum/middleClickOverride`), delete it.
+						current.middleClickOverride = null
 						qdel(changeling)
 						changeling = null
 					SSticker.mode.update_change_icons_removed(src)