Gives Geras Dionae melee armour (#20750)

As title, requested by Diona lore with the intention of making Geras
more viable fighting simplemobs - particularly if you want to play one
as a miner.

This is the same rank of armour as a Vaurca Bulwark, though missing
their substantive brute modifier. This has been implemented as melee
armour instead of a brute modifier so they aren't any less susceptible
to projectiles.

Doesn't apply to Coeus Dionae.

code/modules/mob/living/carbon/human/species/station/diona/diona.dm

@@ -64,6 +64,10 @@
 	pain_messages = list("We're in pain", "We hurt so much", "We can't stand the pain")
 	pain_item_drop_cry = list("creaks loudly and ", "rustles erratically and ", "twitches for a moment and ")
 
+	natural_armor = list(
+		MELEE = ARMOR_MELEE_MEDIUM
+	)
+
 	pain_mod = 0.5
 	grab_mod = 0.6 // Viney Tentacles and shit to cling onto
 	resist_mod = 1.5 // Reasonably stronk, not moreso than an Unathi or robot.

code/modules/mob/living/carbon/human/species/station/diona/diona_subspecies.dm

@@ -13,6 +13,9 @@
 	towards more experienced gestalts as a hand to help guide them. As a result of being more formative and idealistic, Coeus tend to be more pacifistic and less prone towards any kind of \
 	violence, including against more simple-minded creatures such as monkeys."
 
+	// An empty list, so they do not inherit the melee armour of their parent.
+	natural_armor = list()
+
 	slowdown = 0
 	siemens_coefficient = 0.7
 	pain_mod = 2