Miscellaneous minor Horizon map improvements (#21716)

Fixes https://github.com/Aurorastation/Aurora.3/issues/21682
Fixes https://github.com/Aurorastation/Aurora.3/issues/21719

changes:
- bugfix: "Fixes shield diffusers no longer diffusing targeted shield
segments (used for mass driver ejection paths)."
- bugfix: "Moves air alarm hidden behind D3 starboard central hallway
shutters to visible free spot on opposite wall."
  - rscadd: "Adds tintable window control to the Horizon's exam room."
- rscadd: "Adds tintable window controls for both the interior and
exterior windows of the Horizon's recovery room."
- rscadd: "Adds an additional light to a particularly dark corner of the
Horizon's d2 hard storage room."

code/modules/shieldgen/_energy_field.dm

@@ -84,6 +84,13 @@
 			var/obj/effect/energy_field/F = new(T, src)
 			field += F
 
+/**
+ * Removes the field from the managed list and deletes it. Called by shield diffusion.
+ */
+/datum/energy_field/proc/remove_individual_field(var/obj/effect/energy_field/field_to_remove)
+	field.Remove(field_to_remove)
+	qdel(field_to_remove)
+
 /**
  * Adds a bunch of UI data for TGUIs with relevant field data.
  */

code/modules/shieldgen/energy_field.dm

@@ -16,8 +16,6 @@
 	/// The damage suffered by the field.
 	var/damage = 0
 	var/ticks_recovering = 10
-	var/diffused_for = 0
-	var/diffused = FALSE
 	/// If strength goes is 1 or above, this is set to TRUE, this is to prevent flickering and animate being called constantly
 	var/is_strong = FALSE
 
@@ -41,7 +39,7 @@
 	return ..()
 
 /obj/effect/energy_field/proc/diffuse(var/duration)
-	diffused_for = max(duration, 0)
+	energy_field.remove_individual_field(src)
 
 /obj/effect/energy_field/attackby(obj/item/attacking_item, mob/user)
 	user.do_attack_animation(src, attacking_item)
@@ -105,28 +103,17 @@
 		damage = max(damage - energy_field.strengthen_rate, 0)
 
 /obj/effect/energy_field/proc/density_check(var/turn_on)
-	if(turn_on && !diffused)
+	if(turn_on)
 		alpha = 0
 		density = TRUE
 		mouse_opacity = MOUSE_OPACITY_ICON
 		animate(src, 2 SECONDS, alpha = 255)
-	else if(!turn_on)
+	else
 		alpha = 255
 		density = FALSE
 		mouse_opacity = MOUSE_OPACITY_TRANSPARENT
 		animate(src, 2 SECONDS, alpha = 0)
 
-/obj/effect/energy_field/proc/diffuse_check()
-	diffused_for = max(0, diffused_for - 1)
-
-	if(diffused_for && !diffused)
-		diffused = TRUE
-		if(is_strong)
-			density_check(FALSE)
-	else if(!diffused_for && diffused)
-		diffused = FALSE
-		density_check(TRUE)
-
 /obj/effect/energy_field/proc/update_strength()
 	SIGNAL_HANDLER
 	//if we take too much damage, drop out - the generator will bring us back up if we have enough power
@@ -142,8 +129,6 @@
 	if (density != old_density)
 		update_nearby_tiles()
 
-	diffuse_check()
-
 /**
  * Easy helper proc to return the shield's current health.
  */

code/modules/shieldgen/shield_diffuser.dm

@@ -8,8 +8,8 @@
 	icon = 'icons/obj/machinery/shielding.dmi'
 	icon_state = "fdiffuser_on"
 	use_power = POWER_USE_IDLE
-	idle_power_usage = 100
-	active_power_usage = 2000
+	idle_power_usage = 0
+	active_power_usage = 0
 	anchored = TRUE
 	density = FALSE
 	level = 1
@@ -19,20 +19,20 @@
 
 /obj/machinery/shield_diffuser/feedback_hints(mob/user, distance, is_adjacent)
 	. += ..()
-	. += "It is [diffuser_enabled ? "diffuser_enabled" : "disabled"]."
+	. += "It is [diffuser_enabled ? "enabled" : "disabled"]."
 
 /obj/machinery/shield_diffuser/process()
 	if(stat & BROKEN)
 		return PROCESS_KILL
 
-	if(!diffuser_enabled || stat & NOPOWER)
+	if(!diffuser_enabled)
 		return
 
 	for(var/obj/effect/energy_field/S in range(diffuser_range, src))
-		S.diffuse(5)
+		S.diffuse()
 
 /obj/machinery/shield_diffuser/update_icon()
-	if(stat & NOPOWER || stat & BROKEN || !diffuser_enabled)
+	if(stat & BROKEN || !diffuser_enabled)
 		icon_state = "fdiffuser_off"
 	else
 		icon_state = "fdiffuser_on"