Adds Lawyer/HoP/QM/Spy unique traitor item, the briefcase firearm mechanism (#95607)

## About The Pull Request

Lawyers, Quartermasters, and Heads of Personnels can now purchase a
`"Briefcase Embedded Firearm Trigger"` from the traitor uplink for 4 tc.

The briefcase looks like a normal, unassuming briefcase - But when any
weapon is placed inside, you gain the ability to "fire" the briefcase,
which *actually* fires the weapon.

Only the first weapon found is fired, even if it's empty.
So while you CAN put 5 pistols inside, you'd have to cycle them in and
out manually.

This works with *any* weapon that can fit inside the briefcase, which
essentially restricts it to pistols and some laser weapons.
*No*, sniper rifles won't work in the briefcase. (You can't use it to
bypass weapons that require two hands.)
*Yes*, you can also handcuff the briefcase to your wrist as normal. (Who
knows what this will allow.)

---

Also purchaseable is an 8tc `"Briefcase Embedded Firearm (Combo Deal)"`,
which comes pre-loaded with a Makarov and 0 magazines.

This variant is also available to all Spies as a medium difficulty
reward.

--- 

Additionally I changed the boot-dagger's examine tell to only show to
people holding the item.
When I was implementing the briefcase gun I made the examine tell only
show while held and I thought "well, the boot-dagger should follow the
same logic". They're meant to be stealth objects so being able to figure
it out from across the room feels weird.

## Why It's Good For The Game

This was a random idea someone threw out that I thought fit the vibe and
gameplay of traitors and spies really well.
It's a very espionage-y idea, very James Bond. 

It will definitely catch a lot of people off guard. It basically allows
the Lawyer to walk around with a pistol or revolver drawn at all times.
I'm a bit worried it'll be too potent combined with handcuffs (nodrop
revolver?), but the Lawyer doesn't get many Ws so maybe it's fine.

## Changelog

🆑 Melbert
add: Traitor Lawyers, Quartermasters, and Heads of Personnels can now
purchase a "Briefcase Embedded Firearm Trigger" from the uplink for 4tc
- a briefcase that allows any weapon stored within to be fired by
"firing" the briefcase itself. Weapon sizes are restricted to whatever
fits in a briefcase, meaning it practically only works with pistols and
some laser weapons. It has a subtle examine tell that only appears while
being held.
add: Also available for 8tc is a combo deal that comes pre-loaded with a
Makarov. This can also appear as a medium Spy reward.
balance: The Spy item "boot dagger"'s examine tell now only appears if
you're examining them WHILE holding them.
/🆑

code/modules/uplink/uplink_items.dm

@@ -78,7 +78,7 @@
 	/// Whether this can be discounted or not
 	var/cant_discount = FALSE
 	/// If discounted, is true. Used to send a signal to update reimbursement.
-	var/discounted = FALSE
+	VAR_FINAL/discounted = FALSE
 	/// If this value is changed on two items they will share stock, defaults to not sharing stock with any other item
 	var/stock_key = UPLINK_SHARED_STOCK_UNIQUE
 	/// How many items of this stock can be purchased.

code/modules/uplink/uplink_items/job.dm

@@ -14,7 +14,7 @@
 	cost = 2
 	restricted_roles = list(JOB_CURATOR)
 	limited_stock = 1 //please don't spam deadchat
-	surplus = 1 
+	surplus = 1
 
 /datum/uplink_item/role_restricted/mail_counterfeit_kit
 	name = "GLA Brand Mail Counterfeit Kit"
@@ -405,3 +405,32 @@
 	item = /obj/item/emitter_disk/blast
 	cost = 5
 	restricted_roles = list(JOB_STATION_ENGINEER, JOB_CHIEF_ENGINEER)
+
+/datum/uplink_item/role_restricted/briefcase_gun
+	name = "Briefcase Embedded Firearm Trigger"
+	desc = "A briefcase with a firing mechanism built into the handle that connects to the first weapon stored within. \
+		\"Aiming and firing\" the briefcase will instead trigger the firing mechanism, causing the weapon to fire through a discrete hole. \
+		Work with any firearm you could fit inside."
+	item = /obj/item/storage/briefcase/gun
+	purchasable_from = UPLINK_TRAITORS
+	cant_discount = TRUE // remove this when we get uplink logic to have one discount apply to all items on the same stock key
+	cost = 4
+	surplus = 0
+	uplink_item_flags = NONE
+	stock_key = "briefcase_gun"
+	restricted_roles = list(
+		JOB_HEAD_OF_PERSONNEL,
+		JOB_LAWYER,
+		JOB_QUARTERMASTER,
+	)
+
+/datum/uplink_item/role_restricted/briefcase_gun/with_gun
+	name = "Briefcase Embedded Firearm Trigger (Combo Deal)"
+	desc = parent_type::desc + " This COMBO DEAL comes with a pre-loaded Makarov pistol! (No extra magazines, though.)"
+	item = /obj/item/storage/briefcase/gun/preloaded
+	purchasable_from = parent_type::purchasable_from | UPLINK_SPY
+	cost = 8
+	surplus = 50
+	progression_minimum = /datum/uplink_item/dangerous/pistol::progression_minimum
+	population_minimum = /datum/uplink_item/dangerous/pistol::population_minimum
+	relevant_child_items = /datum/uplink_item/dangerous/pistol::relevant_child_items