添加应用级别窗口按钮，以改善linux wayland下系统窗口按钮失效的问题 (#1119)

* feat(window): add app-level window controls with settings toggle

Add a persistent settings toggle to enable app-level minimize/maximize/close controls and hide system decorations when enabled, providing a Wayland-friendly fallback for broken native titlebar interactions.

Co-authored-by: Cursor <cursoragent@cursor.com>

* fix(window): restrict app-level window controls to Linux only and fix startup flicker

- Guard useAppWindowControls with isLinux() in App.tsx so it's always
  false on macOS/Windows even if persisted as true
- Wrap set_decorations call in lib.rs with #[cfg(target_os = "linux")]
- Only show the toggle in WindowSettings on Linux
- Skip setDecorations effect while settingsData is still loading to
  prevent the Rust-side decoration state from being overridden by the
  undefined->false fallback, which caused a brief title bar flicker

---------

Co-authored-by: wzk <wx13571681304@outlook.com>
Co-authored-by: Cursor <cursoragent@cursor.com>
Co-authored-by: Jason <farion1231@gmail.com>

src-tauri/src/settings.rs

@@ -175,6 +175,8 @@ pub struct AppSettings {
     pub show_in_tray: bool,
     #[serde(default = "default_minimize_to_tray_on_close")]
     pub minimize_to_tray_on_close: bool,
+    #[serde(default)]
+    pub use_app_window_controls: bool,
     /// 是否启用 Claude 插件联动
     #[serde(default)]
     pub enable_claude_plugin_integration: bool,
@@ -293,6 +295,7 @@ impl Default for AppSettings {
         Self {
             show_in_tray: true,
             minimize_to_tray_on_close: true,
+            use_app_window_controls: false,
             enable_claude_plugin_integration: false,
             skip_claude_onboarding: false,
             launch_on_startup: false,