fix(theme): 修复主题管理系统逻辑缺陷

- removeTheme() 删除当前活动主题后从 ConfigManager 读取已保存的主题偏好作为回退方案，不再硬编码 'system'
- saveAndApply() 在调用 _applyCustomTheme 前先 setActiveStyle(style)，确保主题应用时使用最新选择的内置样式
- _applyCustomTheme() 返回 bool 表示成败，失败时调用方清除配置中的 custom_theme 避免下次启动循环失败
- importTheme() 增加 self.__lock 保护，消除 TOCTOU 竞态条件
- ThemeManager 新增 CfgKey 导入以支持 removeTheme 读取配置

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/gui/ALSettingsWidget.py

@@ -34,6 +34,7 @@ import managers.config.ConfigManager as ConfigManager
 from managers.log.LogManager import instance as logInstance
 from managers.theme.ThemeManager import(
     getActiveStyle,
+    setActiveStyle,
     instance as themeInstance
 )
 
@@ -47,18 +48,20 @@ from interfaces.ConfigProvider import (
 def _applyCustomTheme(
     name: str,
     fallback_theme: str = "system"
-):
+) -> bool:
 
     if not name:
         themeInstance().clearTheme(fallback_theme)
-        return
+        return True
     try:
         themeInstance().applyTheme(name)
+        return True
     except Exception as e:
         logInstance().getLogger("ALSettingsWidget").warning(
             f"无法应用自定义主题 '{name}'，回退到 {fallback_theme} 外观: {e}"
         )
         themeInstance().clearTheme(fallback_theme)
+        return False
 
 def _themeToReadable(
     need_theme: str
@@ -266,7 +269,9 @@ class ALSettingsWidget(QWidget, Ui_ALSettingsWidget):
         theme, style, custom_theme = self.collectSettings()
         self.__cfg_mgr.set(CfgKey.GLOBAL.APPEARANCE.STYLE, style)
         self.__cfg_mgr.set(CfgKey.GLOBAL.APPEARANCE.CUSTOM_THEME, custom_theme)
-        _applyCustomTheme(custom_theme, theme)
+        setActiveStyle(style)
+        if not _applyCustomTheme(custom_theme, theme):
+            self.__cfg_mgr.set(CfgKey.GLOBAL.APPEARANCE.CUSTOM_THEME, "")
         self.syncRadioFromNeedTheme(custom_theme)
         # Re-read theme after syncRadioFromNeedTheme — the radio may have
         # changed to match the custom theme's need_theme

src/managers/theme/ThemeManager.py

@@ -19,6 +19,7 @@ from PySide6.QtWidgets import (
     QStyleFactory
 )
 
+from interfaces.ConfigProvider import CfgKey
 from managers.config.ConfigManager import instance as configInstance
 from managers.log.LogManager import instance as logInstance
 from utils.ThemeUtils import (
@@ -119,35 +120,36 @@ class ThemeManager:
         if not os.path.isfile(source_path):
             raise FileNotFoundError(source_path)
         ext = os.path.splitext(source_path)[1].lower()
-        if ext == ".qss":
-            name = os.path.splitext(os.path.basename(source_path))[0]
-            dest_path = os.path.join(self.__themes_dir, name + ".altheme")
-            if os.path.exists(dest_path):
-                raise ValueError(f"主题 '{name}' 已存在")
-            wrapQssToAtheme(source_path, dest_path, "both")
-            return name
-        elif ext == ".altheme":
-            with zipfile.ZipFile(source_path, "r") as zf:
-                if "theme.qss" not in zf.namelist():
-                    raise ValueError("无效的 .altheme: 缺少 theme.qss")
-            info = readThemeInfo(source_path)
-            name = info.get("name", os.path.splitext(os.path.basename(source_path))[0])
-            safe_name = os.path.basename(name)
-            dest_path = os.path.join(self.__themes_dir, safe_name + ".altheme")
-            if os.path.exists(dest_path):
-                raise ValueError(f"主题 '{safe_name}' 已存在")
-            # Check for name collision with existing themes by the same author
-            new_author = info.get("author", "")
-            for existing in self.listThemes():
-                if (existing.get("name", "") == safe_name
-                    and existing.get("author", "") == new_author):
-                    raise ValueError(
-                        f"主题名称 '{safe_name}' (作者 '{new_author}') 已存在"
-                    )
-            shutil.copy2(source_path, dest_path)
-            return safe_name
-        else:
-            raise ValueError(f"不支持的文件类型: {ext}")
+        with self.__lock:
+            if ext == ".qss":
+                name = os.path.splitext(os.path.basename(source_path))[0]
+                dest_path = os.path.join(self.__themes_dir, name + ".altheme")
+                if os.path.exists(dest_path):
+                    raise ValueError(f"主题 '{name}' 已存在")
+                wrapQssToAtheme(source_path, dest_path, "both")
+                return name
+            elif ext == ".altheme":
+                with zipfile.ZipFile(source_path, "r") as zf:
+                    if "theme.qss" not in zf.namelist():
+                        raise ValueError("无效的 .altheme: 缺少 theme.qss")
+                info = readThemeInfo(source_path)
+                name = info.get("name", os.path.splitext(os.path.basename(source_path))[0])
+                safe_name = os.path.basename(name)
+                dest_path = os.path.join(self.__themes_dir, safe_name + ".altheme")
+                if os.path.exists(dest_path):
+                    raise ValueError(f"主题 '{safe_name}' 已存在")
+                # Check for name collision with existing themes by the same author
+                new_author = info.get("author", "")
+                for existing in self.listThemes():
+                    if (existing.get("name", "") == safe_name
+                        and existing.get("author", "") == new_author):
+                        raise ValueError(
+                            f"主题名称 '{safe_name}' (作者 '{new_author}') 已存在"
+                        )
+                shutil.copy2(source_path, dest_path)
+                return safe_name
+            else:
+                raise ValueError(f"不支持的文件类型: {ext}")
 
     def listThemes(
         self
@@ -214,7 +216,10 @@ class ThemeManager:
                 os.remove(filepath)
                 if self.__current_theme_name == name:
                     self.__current_theme_name = ""
-                    self.clearTheme("system")
+                    saved_theme = configInstance().get(
+                        CfgKey.GLOBAL.APPEARANCE.THEME, "system"
+                    )
+                    self.clearTheme(saved_theme)
 
     def applyTheme(
         self,