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_031_open_ocean/kq4_031_open_ocean.gd

@@ -21,6 +21,10 @@ func _on_ocean_near_island_interacted() -> void:
 	$kq4_032_ocean_near_island.default_script(self)
 
 
+func _on_desert_island_interacted() -> void:
+	$kq4_043_desert_island.default_script(self)
+
+
 func _on_room_looked() -> void:
 	start_main_script(ScriptBuilder.init(
 		ScriptBuilder.narrate("You are swimming in a great ocean. Playful fish leap about you as you swim.")