[MIRROR] Mech mob deletion fix (#1884)

* Mech mob deletion fix (#82415)

## About The Pull Request

If the occupant of a mech has their mob changed -- mutation, polymorph,
admin fuckery -- or if a mob somehow enters a mech without becoming an
occupant -- the above, or a chestburster in said mech pilot -- then they
don't get added to the occupants, only the contents. All contents are
hard-deleted if a mech is destroyed. This fixes that, and ejects any
mobs inside mechs who are technically inside the mech but not an
occupant.
## Why It's Good For The Game

Fixes #82395 and any similar case
## Changelog

Being inside a mech when it's destroyed should no longer delete you,
even if you ended up in that mech in an odd way.
:cl: Bisar
fix: Mechs will no longer delete their living non-occupant contents when
destroyed.
/:cl:

* Mech mob deletion fix

---------

Co-authored-by: Joshua Kidder <[email protected]>

code/modules/vehicles/mecha/_mecha.dm

@@ -269,8 +269,12 @@
 	AddElement(/datum/element/hostile_machine)
 
 /obj/vehicle/sealed/mecha/Destroy()
-	for(var/ejectee in occupants)
-		mob_exit(ejectee, silent = TRUE)
+	/// If the former occupants get polymorphed, mutated, chestburstered,
+	/// or otherwise replaced by another mob, that mob is no longer in .occupants
+	/// and gets deleted with the mech. However, they do remain in .contents
+	var/list/potential_occupants = contents ^ occupants
+	for(var/mob/buggy_ejectee in potential_occupants)
+		mob_exit(buggy_ejectee, silent = TRUE)
 
 	if(LAZYLEN(flat_equipment))
 		for(var/obj/item/mecha_parts/mecha_equipment/equip as anything in flat_equipment)

code/modules/vehicles/mecha/mecha_mob_interaction.dm

@@ -139,6 +139,8 @@
 			mob_container = AI
 			newloc = get_turf(AI.linked_core)
 			qdel(AI.linked_core)
+	else if(isliving(M))
+		mob_container = M
 	else
 		return ..()
 	var/mob/living/ejector = M