Mob ckey sanity check now respects insano aghost code (#91517)

## About The Pull Request

I HATE THIS PLACE DUDE, aghosting sets your ckey/key to your normal
ckey/ckey but with @ prefixed. hhhhhhhhh.

code/__DEFINES/client.dm

@@ -10,3 +10,6 @@
 /// The maximum client BYOND build to disable screentip icons for.
 /// Update this whenever https://www.byond.com/forum/post/2967731 is fixed.
 #define MAX_BYOND_BUILD_DISABLE_SCREENTIP_ICONS 1699
+
+/// Aghosting AND APPERANTLY STEALTHMINNING sets your ckey/key == "@[old_key]" because it hates me. this detects that
+#define IS_FAKE_KEY(key) (key && key[1] == "@")

code/modules/admin/verbs/adminpm.dm

@@ -741,7 +741,7 @@ ADMIN_VERB(cmd_admin_pm_panel, R_NONE, "Admin PM", "Show a list of clients to PM
 		return null
 
 	var/searching_ckey = whom
-	if(whom[1] == "@")
+	if(IS_FAKE_KEY(whom))
 		searching_ckey = findTrueKey(whom)
 
 	if(searching_ckey == EXTERNAL_PM_USER)

code/modules/mob/dead/observer/observer.dm

@@ -259,7 +259,7 @@ Works together with spawning an observer, noted above.
 /mob/proc/ghostize(can_reenter_corpse = TRUE, admin_ghost = FALSE)
 	if(!key)
 		return
-	if(key[1] == "@") // Skip aghosts.
+	if(IS_FAKE_KEY(key)) // Skip aghosts.
 		return
 
 	if(HAS_TRAIT(src, TRAIT_CORPSELOCKED) && !admin_ghost)
@@ -375,7 +375,7 @@ This is the proc mobs get to turn into a ghost. Forked from ghostize due to comp
 	if(!can_reenter_corpse && !mind.has_antag_datum(/datum/antagonist/changeling)) //SKYRAT EDIT
 		to_chat(src, span_warning("You cannot re-enter your body."))
 		return
-	if(mind.current.key && mind.current.key[1] != "@") //makes sure we don't accidentally kick any clients
+	if(mind.current.key && !IS_FAKE_KEY(mind.current.key)) //makes sure we don't accidentally kick any clients
 		to_chat(usr, span_warning("Another consciousness is in your body...It is resisting you."))
 		return
 	client.view_size.setDefault(getScreenSize(client.prefs.read_preference(/datum/preference/toggle/widescreen)))//Let's reset so people can't become allseeing gods

code/modules/mob/living/carbon/carbon.dm

@@ -898,7 +898,7 @@
 	if (current_brain.suicided || (current_brain.brainmob && HAS_TRAIT(current_brain.brainmob, TRAIT_SUICIDED)))
 		return DEFIB_FAIL_NO_INTELLIGENCE
 
-	if(key && key[1] == "@") // Adminghosts
+	if(IS_FAKE_KEY(key))
 		return DEFIB_NOGRAB_AGHOST
 
 	return DEFIB_POSSIBLE

code/modules/mob/mob.dm

@@ -26,7 +26,7 @@
 /mob/Destroy()
 	if(client)
 		stack_trace("Mob with client has been deleted.")
-	else if(ckey)
+	else if(ckey && !IS_FAKE_KEY(ckey)) // FUCK YOU AGHOST CODE FUCK YOU
 		stack_trace("Mob without client but with associated ckey, [ckey], has been deleted.")
 
 	persistent_client?.set_mob(null)

code/modules/spells/spell_types/pointed/mind_transfer.dm

@@ -112,7 +112,7 @@
 		|| mind_to_swap.has_antag_datum(/datum/antagonist/cult) \
 		|| mind_to_swap.has_antag_datum(/datum/antagonist/changeling) \
 		|| mind_to_swap.has_antag_datum(/datum/antagonist/rev) \
-		|| mind_to_swap.key?[1] == "@" \
+		|| IS_FAKE_KEY(mind_to_swap.key) \
 	)
 		to_chat(caster, span_warning("[to_swap.p_Their()] mind is resisting your spell!"))
 		return FALSE