Sign/plaque contextual screentips and file reorganizing (#73246)

## About The Pull Request

This PR adds contextual screen tips to signs and plaques based on the
held tool. Wrenches unfasten, and welders repair. Behaves the same with
plaques, but plaques also get a screentip for using a fountain pen on
them if they can be engraved. Also adds a tip to editable-item signs
with a pen out.
Tested to avoid issues with posters from cropping up, and it appears to
still behave correctly with paper posters, which are apparently a type
of sign. Go figure.


![image](https://user-images.githubusercontent.com/41715314/216807994-c2400fa0-77fa-48e9-8c2e-5c5ea660a1d8.png)

I've also reorganized the sign and plaque files to follow our more
standard object hierarchy of base type -> inherited procs -> subtype
specific procs, where these were interspersed throughout the file. I did
however leave the armor datums below the object, as they appear to
follow new convention.

## Why It's Good For The Game

Screentips avoid ambiguity and improve readability of construction. Easy
improvement.

Plus, improves consistency of the signs file layout-wise.

## Changelog

🆑
qol: Adds screentips to both signs and plaque construction/modification.
/🆑

code/game/objects/structures/plaques/_plaques.dm

@@ -18,27 +18,22 @@
 	fire = 50
 	acid = 50
 
-/obj/item/plaque //The item version of the above.
-	icon = 'icons/obj/signs.dmi'
-	icon_state = "blankplaque"
-	inhand_icon_state = "blankplaque"
-	lefthand_file = 'icons/mob/inhands/items_lefthand.dmi'
-	righthand_file = 'icons/mob/inhands/items_righthand.dmi'
-	name = "blank plaque"
-	desc = "A blank plaque, use a fancy pen to engrave it. It can be placed on a wall."
-	w_class = WEIGHT_CLASS_NORMAL
-	custom_materials = list(/datum/material/gold = 2000)
-	max_integrity = 200
-	armor_type = /datum/armor/item_plaque
-	///This points the item to make the proper structure when placed on a wall.
-	var/plaque_path = /obj/structure/plaque
-	///Custom plaque structures and items both start "unengraved", once engraved with a fountain pen their text can't be altered again.
-	var/engraved = FALSE
+/obj/structure/plaque/Initialize(mapload)
+	. = ..()
+	register_context()
 
-/datum/armor/item_plaque
-	melee = 50
-	fire = 50
-	acid = 50
+/obj/structure/plaque/add_context(atom/source, list/context, obj/item/held_item, mob/user)
+	. = ..()
+	switch (held_item?.tool_behaviour)
+		if (TOOL_WELDER)
+			context[SCREENTIP_CONTEXT_LMB] = "Repair"
+			return CONTEXTUAL_SCREENTIP_SET
+		if (TOOL_WRENCH)
+			context[SCREENTIP_CONTEXT_LMB] = "Unfasten"
+			return CONTEXTUAL_SCREENTIP_SET
+	if(istype(held_item, /obj/item/pen/fountain) && !engraved)
+		context[SCREENTIP_CONTEXT_LMB] = "Engrave"
+		return CONTEXTUAL_SCREENTIP_SET
 
 /obj/structure/plaque/attack_hand(mob/user, list/modifiers)
 	. = ..()
@@ -85,24 +80,6 @@
 	atom_integrity = max_integrity
 	return TRUE
 
-/obj/item/plaque/welder_act(mob/living/user, obj/item/I)
-	. = ..()
-	if(user.combat_mode)
-		return FALSE
-	if(atom_integrity == max_integrity)
-		to_chat(user, span_warning("This plaque is already in perfect condition."))
-		return TRUE
-	if(!I.tool_start_check(user, amount=0))
-		return TRUE
-	user.visible_message(span_notice("[user] starts repairing [src]..."), \
-		span_notice("You start repairing [src]."))
-	if(!I.use_tool(src, user, 4 SECONDS, volume = 50))
-		return TRUE
-	user.visible_message(span_notice("[user] finishes repairing [src]."), \
-		span_notice("You finish repairing [src]."))
-	atom_integrity = max_integrity
-	return TRUE
-
 /obj/structure/plaque/attackby(obj/item/I, mob/user, params)
 	if(istype(I, /obj/item/pen/fountain))
 		if(engraved)
@@ -135,6 +112,47 @@
 		return
 	return ..()
 
+/obj/item/plaque //The item version of the above.
+	icon = 'icons/obj/signs.dmi'
+	icon_state = "blankplaque"
+	inhand_icon_state = "blankplaque"
+	lefthand_file = 'icons/mob/inhands/items_lefthand.dmi'
+	righthand_file = 'icons/mob/inhands/items_righthand.dmi'
+	name = "blank plaque"
+	desc = "A blank plaque, use a fancy pen to engrave it. It can be placed on a wall."
+	w_class = WEIGHT_CLASS_NORMAL
+	custom_materials = list(/datum/material/gold = 2000)
+	max_integrity = 200
+	armor_type = /datum/armor/item_plaque
+	///This points the item to make the proper structure when placed on a wall.
+	var/plaque_path = /obj/structure/plaque
+	///Custom plaque structures and items both start "unengraved", once engraved with a fountain pen their text can't be altered again.
+	var/engraved = FALSE
+
+/datum/armor/item_plaque
+	melee = 50
+	fire = 50
+	acid = 50
+
+/obj/item/plaque/welder_act(mob/living/user, obj/item/I)
+	. = ..()
+	if(user.combat_mode)
+		return FALSE
+	if(atom_integrity == max_integrity)
+		to_chat(user, span_warning("This plaque is already in perfect condition."))
+		return TRUE
+	if(!I.tool_start_check(user, amount=0))
+		return TRUE
+	user.visible_message(span_notice("[user] starts repairing [src]..."), \
+		span_notice("You start repairing [src]."))
+	if(!I.use_tool(src, user, 4 SECONDS, volume = 50))
+		return TRUE
+	user.visible_message(span_notice("[user] finishes repairing [src]."), \
+		span_notice("You finish repairing [src]."))
+	atom_integrity = max_integrity
+	return TRUE
+
+
 /obj/item/plaque/attackby(obj/item/I, mob/user, params) //Same as part of the above, except for the item in hand instead of the structure.
 	if(istype(I, /obj/item/pen/fountain))
 		if(engraved)