feat: Implement tile scarcity model for tile generation and power-up inventory UI for player interaction.

scripts/models/scarcity_model.gd

@@ -50,7 +50,10 @@ static func get_tile_weights() -> Dictionary:
 		weights[tile] = STANDARD_WEIGHT
 		
 	# Special tiles
+	var is_sng = LobbyManager.game_mode == "Stop n Go"
 	for tile in SPECIAL_TILES:
+		if is_sng and tile == TILE_FREEZE:
+			continue # Hide Wall Block only in Stop n Go
 		weights[tile] = special_weight
 		
 	return weights