Cleanups and tweaks observer code (#30250)

* observer cleanup

* this

* bit more

* Update tgui.bundle.js

code/modules/events/blob/overmind.dm

@@ -4,7 +4,7 @@
 	icon = 'icons/mob/blob.dmi'
 	icon_state = "marker"
 
-	invisibility = INVISIBILITY_OBSERVER
+	invisibility = INVISIBILITY_HIGH
 	lighting_alpha = LIGHTING_PLANE_ALPHA_MOSTLY_INVISIBLE
 	mouse_opacity = MOUSE_OPACITY_OPAQUE
 

code/modules/events/immovable_rod.dm

@@ -63,7 +63,7 @@ In my current plan for it, 'solid' will be defined as anything with density == 1
 	if(href_list["follow"])
 		var/mob/dead/observer/ghost = usr
 		if(istype(ghost))
-			ghost.ManualFollow(src)
+			ghost.manual_follow(src)
 
 /obj/effect/immovablerod/Destroy()
 	GLOB.poi_list.Remove(src)