Mechanical Engineering Cross Role Interactions (#22880)

<img width="606" height="144" alt="image"
src="https://github.com/user-attachments/assets/f1c88863-37be-41e0-be79-27fca980a3f3"
/>

This PR adds new "Cross-Role Interactions" for the Mechanical
Engineering skill, with two specific kinds that are aimed at a variety
of different roles.

1. **Bonus damage vs. structures**: Having ranks in MechE makes you deal
bonus damage when melee attacking structures like Airlocks and Windows.
This makes it a desireable niche pick for any kind of job that can see
themself wanting to take a breaching to a room's entrance! For example,
paramedics, shaft miners, and security can all make use of it on
occasion.
2. **Mech Repair Speed**: This one is aimed specifically at Machinists.
Repairing mechs with a welder is no longer instantaneous (That was very
powergamey in practice for 'battle machinists'). Instead it has a repair
speed (and repair amount) that scales with your Mechanical Engineering
skill.

Why MechE and not Robotics? To encourage further "Machinist
Specialization". Machinist players were already pretty naturally
inclined to position their character as either being a Robotics
Specialist, or a Mechatronics Specialist, by sheer virtue of there being
two machinist slots and two noticeably distinctive roles. This
separation of skill interactions is there to further encourage this
degree of separation between machinist skillsets.

As a side note, just so I'm not thoroughly pissing off every machinist
main. As a quality of life improvement, I've made it so that attempting
to repair a mech with a welder will loop the repair until completed or
interrupted.

---------

Signed-off-by: VMSolidus <evilexecutive@gmail.com>

code/modules/heavy_vehicle/components/_components.dm

@@ -139,7 +139,7 @@
 /obj/item/mech_component/proc/update_components()
 	return
 
-/obj/item/mech_component/proc/repair_brute_generic(var/obj/item/weldingtool/WT, var/mob/user)
+/obj/item/mech_component/proc/repair_brute_generic(obj/item/weldingtool/WT, var/mob/user)
 	if(!istype(WT))
 		return
 	if(!brute_damage)
@@ -148,12 +148,38 @@
 	if(!WT.isOn())
 		to_chat(user, SPAN_WARNING("Turn \the [WT] on, first."))
 		return
-	if(WT.use(0, user))
-		var/repair_value = 15
-		if(brute_damage)
-			repair_brute_damage(repair_value)
-			to_chat(user, SPAN_NOTICE("You mend the damage to \the [src]."))
-			playsound(user.loc, 'sound/items/Welder.ogg', 25, 1)
+
+	var/do_after_time = 5 SECONDS
+	var/repair_value = 5
+	// Get modifiers only once before entering the loop.
+	SEND_SIGNAL(user, COMSIG_GET_MECH_WELD_MODIFIERS, src, &do_after_time, &repair_value)
+	if (repair_value <= 0) // Sanity check just in case to prevent an infinite loop after we start.
+		to_chat(user, SPAN_NOTICE("You can't repair \the [src]"))
+		return
+
+	to_chat(user, SPAN_NOTICE("You start welding \the [src]"))
+	playsound(user.loc, 'sound/items/Welder.ogg', 25, 1)
+
+	// Loop until finished fixing it.
+	while (TRUE)
+		if (!src || !WT || !user) // Any one of the three failed to exist.
+			return
+
+		if (!brute_damage) // Check damage both before and after do_after
+			to_chat(user, SPAN_NOTICE("You finish welding \the [src]."))
+			return
+
+		if (!do_after(user, do_after_time, src, DO_DEFAULT | DO_USER_UNIQUE_ACT | DO_SHOW_PROGRESS))
+			to_chat(user, SPAN_NOTICE("You were interrupted while welding \the [src]"))
+			return
+
+		if (!brute_damage || !WT.use(0, user))
+			to_chat(user, SPAN_NOTICE("You finish welding \the [src]."))
+			return
+
+		repair_brute_damage(repair_value)
+		to_chat(user, SPAN_NOTICE("You mend the damage to \the [src]."))
+		playsound(user.loc, 'sound/items/Welder.ogg', 25, 1)
 
 /obj/item/mech_component/proc/repair_burn_generic(var/obj/item/stack/cable_coil/CC, var/mob/user)
 	if(!istype(CC))