Implement 40250 classic client port

project/ui/system_option_ui.gd

@@ -45,6 +45,15 @@ var camera_mode := 1     # 0 近, 1 远
 var fog_level := 1       # 0 浓, 1 中, 2 淡
 var tiling_mode := 1     # 0 CPU, 1 GPU（占位）
 
+static func config_path() -> String:
+	var override_dir := OS.get_environment("MT_CONFIG_DIR")
+	if override_dir != "":
+		return override_dir.path_join("system_option.cfg")
+	# Godot headless 在受限执行环境里可能无法写 user://；测试配置放在系统
+	# 临时目录，正常图形客户端仍使用 user://。
+	return OS.get_temp_dir().path_join("mtgodot_system_option.cfg") \
+		if DisplayServer.get_name() == "headless" else CFG_PATH
+
 func setup(ui_manager: CanvasLayer, assets: String, audio_node: Node = null,
 		cam_getter := Callable(), env_getter := Callable()) -> void:
 	ui = ui_manager
@@ -228,7 +237,7 @@ func _apply_fog() -> void:
 # --- persistence (= systemSetting 配置文件) --------------------------
 
 func _load_cfg() -> void:
-	if _cfg.load(CFG_PATH) != OK:
+	if _cfg.load(config_path()) != OK:
 		return
 	music_volume = float(_cfg.get_value("audio", "music_volume", music_volume))
 	sound_volume = float(_cfg.get_value("audio", "sound_volume", sound_volume))
@@ -242,4 +251,6 @@ func _save() -> void:
 	_cfg.set_value("video", "camera_mode", camera_mode)
 	_cfg.set_value("video", "fog_level", fog_level)
 	_cfg.set_value("video", "tiling_mode", tiling_mode)
-	_cfg.save(CFG_PATH)
+	var err := _cfg.save(config_path())
+	if err != OK:
+		push_warning("SystemOptionUI: save failed (%s): %s" % [err, config_path()])