Adds gladiuses (gladii?) (#93631)

## About The Pull Request

Adds the Gladius alongside its scabbard. Replaces undead roman
legionarries' claymores with gladii.
<img width="152" height="105" alt="image"
src="https://github.com/user-attachments/assets/fdd21960-0f73-4564-b381-7044838a0f51"
/>
<img width="194" height="165" alt="image"
src="https://github.com/user-attachments/assets/a3f602e1-9ce6-4ded-b40d-d7088da292c9"
/>
<img width="136" height="133" alt="image"
src="https://github.com/user-attachments/assets/e8105ba3-d1e5-42cb-86e5-16db6edd56f7"
/>


## Why It's Good For The Game

This started as me thinking "hmmm those guys shouldn't have longswords"
and so I gave them the gladius, the famous standard issue foot soldier
weapon for the roman army. It's better in that it's more historically
accurate, which is definitely something everyone cares about a lot.

## Changelog
🆑
add: Roman skeletons now have Roman swords.
/🆑

---------

Co-authored-by: die <96586172+grungussuss@users.noreply.github.com>

code/game/objects/items/storage/belt.dm

@@ -640,6 +640,15 @@
 	worn_icon_state = "grass_sheath"
 	storage_type = /datum/storage/green_sabre_belt
 
+/obj/item/storage/belt/sheath/gladius
+	name = "gladius scabbard"
+	desc = "A fun-sized sheath for a fun-sized sword."
+	icon_state = "gladius_sheath"
+	inhand_icon_state = "gladius_sheath"
+	worn_icon_state = "gladius_sheath"
+	storage_type = /datum/storage/gladius_belt
+	stored_blade = /obj/item/claymore/gladius
+
 /obj/item/storage/belt/plant
 	name = "botanical belt"
 	desc = "A sturdy leather belt used to hold most hydroponics supplies."