Makes your current position clearer while jaunting (#90173)

## About The Pull Request

I was fucking around testing the Voidwalker earlier for a different
issue and didn't like that I couldn't see myself while in space.
This PR makes it so that Voidwalkers and also any variant of Ethereal
Jaunt place an icon visible only to you at your current position (it's
like your _soul_) so that you can see where you are going.
Nobody else can see it.


![dreamseeker_qCXrCwHaUW](https://github.com/user-attachments/assets/3d6d1136-1658-4701-af78-057b2cfeb059)

![dreamseeker_hqH73zu66P](https://github.com/user-attachments/assets/4f620711-9a1a-4f8e-be3b-1c3367b9f9dc)



There are almost certainly some other sources of being invisible which
could use this so let me know if you are aware of one.
Although if you do that I may need to make my code more generic.

## Why It's Good For The Game

It's nice to be able to see where you are precisely rather than just it
being the centre of the screen

## Changelog

🆑
qol: It is now easier to see where you currently are while jaunting
/🆑

code/game/objects/effects/phased_mob.dm

@@ -1,16 +1,22 @@
 /obj/effect/dummy/phased_mob
-	name = "water"
+	name = "ethereal form"
 	anchored = TRUE
 	flags_1 = PREVENT_CONTENTS_EXPLOSION_1
 	resistance_flags = LAVA_PROOF | FIRE_PROOF | UNACIDABLE | ACID_PROOF | SHUTTLE_CRUSH_PROOF
 	invisibility = INVISIBILITY_OBSERVER
 	movement_type = FLOATING
-	/// The movable which's jaunting in this dummy
+	/// The movable which is jaunting in this dummy
 	var/atom/movable/jaunter
 	/// The delay between moves while jaunted
 	var/movedelay = 0
 	/// The speed of movement while jaunted
 	var/movespeed = 0
+	/// Image we show to our jaunter so they can see where they are
+	var/image/position_indicator
+	/// Icon we draw our position indicator from
+	var/phased_mob_icon = 'icons/obj/weapons/guns/projectiles.dmi'
+	/// Icon state we use for our position indicator
+	var/phased_mob_icon_state = "ice_1"
 
 /obj/effect/dummy/phased_mob/Initialize(mapload, atom/movable/jaunter)
 	. = ..()
@@ -21,13 +27,25 @@
 /obj/effect/dummy/phased_mob/proc/set_jaunter(atom/movable/new_jaunter)
 	jaunter = new_jaunter
 	jaunter.forceMove(src)
-	if(ismob(jaunter))
-		var/mob/mob_jaunter = jaunter
-		RegisterSignal(mob_jaunter, COMSIG_MOB_STATCHANGE, PROC_REF(on_stat_change))
-		mob_jaunter.reset_perspective(src)
+	if(!ismob(jaunter))
+		return
+	var/mob/mob_jaunter = jaunter
+	position_indicator = image(phased_mob_icon, src, phased_mob_icon_state, ABOVE_LIGHTING_PLANE)
+	position_indicator.appearance_flags |= RESET_ALPHA
+	SET_PLANE_EXPLICIT(position_indicator, ABOVE_LIGHTING_PLANE, src)
+	RegisterSignal(mob_jaunter, COMSIG_MOB_LOGIN, PROC_REF(show_client_image))
+	RegisterSignal(mob_jaunter, COMSIG_MOB_STATCHANGE, PROC_REF(on_stat_change))
+	mob_jaunter.reset_perspective(src)
+	show_client_image(mob_jaunter)
+
+/// Displays our position indicator to a client
+/obj/effect/dummy/phased_mob/proc/show_client_image(mob/show_to)
+	SIGNAL_HANDLER
+	show_to.client?.images |= position_indicator
 
 /obj/effect/dummy/phased_mob/Destroy()
 	jaunter = null // If a mob was left in the jaunter on qdel, they'll be dumped into nullspace
+	position_indicator = null
 	return ..()
 
 /// Removes [jaunter] from our phased mob
@@ -57,6 +75,7 @@
 	. = ..()
 	if(gone == jaunter)
 		UnregisterSignal(jaunter, COMSIG_MOB_STATCHANGE)
+		UnregisterSignal(jaunter, COMSIG_MOB_LOGIN)
 		SEND_SIGNAL(src, COMSIG_MOB_EJECTED_FROM_JAUNT, jaunter)
 		jaunter = null