feat: Implement core lobby system including UI, player management, and game mode settings.

scripts/managers/playerboard_manager.gd

@@ -370,7 +370,18 @@ func auto_put_item() -> bool:
 			var pos = neighbor.position
 			var cell_3d = Vector3i(pos.x, 1, pos.y)
 			if enhanced_gridmap.get_cell_item(cell_3d) == -1 and not player.is_position_occupied(pos):
-				valid_put_positions.append(pos)
+				# TEKTON DOORS: Avoid portal doors
+				var is_on_portal = false
+				if LobbyManager.is_game_mode(GameMode.Mode.TEKTON_DOORS):
+					var doors = get_tree().get_nodes_in_group("PortalDoors")
+					for door in doors:
+						var door_grid = enhanced_gridmap.local_to_map(enhanced_gridmap.to_local(door.global_position))
+						if Vector2i(door_grid.x, door_grid.z) == pos:
+							is_on_portal = true
+							break
+				
+				if not is_on_portal:
+					valid_put_positions.append(pos)
 
 	if valid_put_positions.is_empty():
 		return false