Create room 043 (Desert Island) and wire to room 031

- Added kq4_043_desert_island scene with 4 exits (north, east, south, west) to room 031
- Updated room 031 to add transition to room 043 (bidirectional connection)
- All 4 exits from room 043 validated with exit checker

scenes/kq4_043_desert_island/kq4_043_desert_island.gd

@@ -0,0 +1,6 @@
+extends Scene
+
+
+func _on_open_ocean_interacted() -> void:
+	# All four exits (north, east, south, west) go to room 031
+	$kq4_031_open_ocean_north.default_script(self)