Changes wall leaning into a component, makes windows leanable (#85771)

## About The Pull Request

Requires #85491 to be merged first, as otherwise leaning on directional
windows looks incredibly goofy
You can now lean on both fulltile and directional windows, and its
possible to easily extend this functionality to other objects. Dunno if
this even deserves to be called a refactor so not marking it in any way.

## Why It's Good For The Game

Just makes sense that you'd be able to do it

## Changelog
🆑
add: You can now lean on windows the same way you can lean on walls
fix: You no longer stop leaning on walls after clicking on anything
/🆑

code/game/objects/structures/windows/window.dm

@@ -41,6 +41,8 @@
 	var/datum/material/glass_material_datum = /datum/material/glass
 	/// Whether or not we're disappearing but dramatically
 	var/dramatically_disappearing = FALSE
+	/// If we added a leaning component to ourselves
+	var/added_leaning = FALSE
 
 /datum/armor/structure_window
 	melee = 50
@@ -90,6 +92,24 @@
 	if (flags_1 & ON_BORDER_1)
 		AddElement(/datum/element/connect_loc, loc_connections)
 
+/obj/structure/window/mouse_drop_receive(atom/dropping, mob/user, params)
+	. = ..()
+	if (added_leaning)
+		return
+	/// For performance reasons and to cut down on init times we are "lazy-loading" the leaning component when someone drags their sprite onto us, and then calling dragging code again to trigger the component
+	AddComponent(/datum/component/leanable, 11, same_turf = (flags_1 & ON_BORDER_1), lean_check = CALLBACK(src, PROC_REF(lean_check)))
+	added_leaning = TRUE
+	dropping.base_mouse_drop_handler(src, null, null, params)
+
+/obj/structure/window/proc/lean_check(mob/living/leaner, list/modifiers)
+	if (!(flags_1 & ON_BORDER_1))
+		return TRUE
+
+	if (leaner.loc == loc)
+		return dir == REVERSE_DIR(leaner.dir)
+
+	return get_dir(src, leaner) == dir && leaner.dir == dir
+
 /obj/structure/window/setDir(newdir)
 	. = ..()
 	if(fulltile)