Avalonia12 (#7)

* ava12升级

* Enable centralized package versioning

Add <Project> and <PropertyGroup> with <ManagePackageVersionsCentrally>true</ManagePackageVersionsCentrally> to Directory.Packages.props to enable centralized package version management across the repository. This allows package versions to be controlled from this single file instead of individual project files.

* Migrate codebase to Avalonia 12 APIs

Apply Avalonia 12 migration changes: replace SystemDecorations with WindowDecorations and remove ExtendClientAreaChromeHints/ExtendClientAreaTitleBarHeightHint usages; update BindingPlugins removal logic (no-op); switch clipboard usage to ClipboardExtensions.SetTextAsync; update Bitmap.CopyPixels calls to the new signature. Replace TextBox.Watermark with PlaceholderText, convert NumberBox styles to FANumberBox and adjust templates, change Checked/Unchecked handlers to IsCheckedChanged, and adapt FluentIcons usages (SymbolIconSource -> FASymbol/FAFont/FluentIcon equivalents). Fix MainWindow partial classes to inherit Window and correct missing variables/fields/usings. Add migration docs/specs/tasks under .trae and include a small TestFluentIcons project for icon testing.

* Migrate to Avalonia 12 and Plugin SDK v5

Upgrade project to the Avalonia 12 baseline and Plugin SDK v5: centralize Avalonia packages, remove legacy WebView.Avalonia usage (use NativeWebView/WebView2 EnvironmentRequested), and update Fluent/Material icon/package usages. Bump multiple package/project versions to 5.0.0 and Avalonia 12.0.1, update plugin template and README/docs to SDK v5, and add PLUGIN_SDK_V5_MIGRATION.md.

Also fix runtime/behavior bugs: make DataLocationResolver use a fixed bootstrap launcher data path and avoid recursive ResolveDataRoot; add legacy-state handling and extraction in OobeStateService; and update component settings tests to reflect migrated storage (DB/backup) and reset cache for test reloads. Various csproj, tests, and docs updated to reflect the migration and ensure build/test compatibility.

* Update icon glyphs and symbol mappings

Replace and refine icon sources across settings pages and controls: many FAFontIconSource glyphs were updated to specific Seagull Fluent Icons codepoints, some FASymbolIconSource usages were replaced with FAFontIconSource, and a number of symbol-to-Symbol enum mappings were adjusted (e.g. "Bell" -> AlertOn, "Shield" -> ShieldLock). Also clarified a comment in SettingsWindow and fixed a trailing newline in StudySettingsPage. Changes standardize icon visuals and bridge FluentIcons glyphs into FluentAvalonia icon sources.

* fix.修复合并产生的问题。

.trae/documents/avalonia12-migration-plan.md

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+# Avalonia 12 迁移计划
+
+## 当前状态
+
+项目已完成以下迁移准备：
+
+* `Directory.Packages.props` 中 Avalonia 包已升级到 `12.0.1`
+
+* `FluentAvaloniaUI` 已升级到 `3.0.0-preview1`
+
+* `Avalonia.Diagnostics` 已替换为 `AvaloniaUI.DiagnosticsSupport`
+
+* `Avalonia.Controls.WebView` 已升级到 `12.0.0`
+
+* `ClassIsland.Markdown.Avalonia` 已升级到 `12.0.0`
+
+## 构建错误清单（26 errors）
+
+### 1. 窗口装饰 API 移除（8 errors）
+
+**文件**：`LanMountainDesktop/Views/SettingsWindow.axaml.cs`（4 errors）
+
+* `ExtendClientAreaChromeHints` 不存在（line 166, 179）
+
+* `SystemDecorations` 已过时，需改用 `WindowDecorations`（line 168, 177）
+
+**文件**：`LanMountainDesktop/Views/ComponentEditorWindow.axaml.cs`（4 errors）
+
+* `ExtendClientAreaChromeHints` 不存在（line 63, 72）
+
+* `SystemDecorations` 已过时，需改用 `WindowDecorations`（line 65, 70）
+
+**AXAML 文件**：13 个文件使用 `SystemDecorations` 属性（编译警告）
+
+### 2. 变量/字段未找到（8 errors）
+
+**文件**：`LanMountainDesktop/Views/MainWindow.ComponentSystem.cs`
+
+* `centerLeft` 不存在（line 759, 766, 778）
+
+* `positions` 不存在（line 1266）
+
+**文件**：`LanMountainDesktop/Views/MainWindow.DesktopPaging.cs`
+
+* `child` 不存在（line 312）
+
+* `_isThreeFingerOrRightDragSwipeActive` 不存在（line 517, 828, 847, 850）
+
+### 3. API 变更（3 errors）
+
+**文件**：`LanMountainDesktop/App.axaml.cs`
+
+* `BindingPlugins` 不可访问（line 532, 537）
+
+**文件**：`LanMountainDesktop/Views/Components/DesktopComponentFailureView.cs`
+
+* `IClipboard.SetTextAsync` 不存在（line 187）
+
+**文件**：`LanMountainDesktop/Services/MonetColorService.cs`
+
+* `Bitmap.CopyPixels` 参数不匹配（line 91）
+
+### 4. 第三方库变更（1 error）
+
+**文件**：`LanMountainDesktop/Views/SettingsWindow.axaml.cs`
+
+* `FluentIcons.Avalonia.SymbolIconSource` 不存在（line 215）
+
+### 5. 过时属性警告（需同步修复）
+
+* `TextBox.Watermark` → `PlaceholderText`（7 处 .cs + 7 处 .axaml）
+
+## 迁移步骤
+
+### Phase 1: 修复窗口装饰 API（高优先级）
+
+1. 重写 `SettingsWindow.ApplyChromeMode()` 使用 Avalonia 12 新 API
+2. 重写 `ComponentEditorWindow.ApplyChromeMode()` 使用 Avalonia 12 新 API
+3. 批量替换所有 `.axaml` 中的 `SystemDecorations` → `WindowDecorations`
+
+### Phase 2: 修复 MainWindow 编译错误（高优先级）
+
+1. 检查 `MainWindow.ComponentSystem.cs` 中 `centerLeft` 和 `positions` 的作用域问题
+2. 检查 `MainWindow.DesktopPaging.cs` 中 `child` 和 `_isThreeFingerOrRightDragSwipeActive` 的作用域问题
+3. 确认这些变量是否被意外删除或重命名
+
+### Phase 3: 修复 Avalonia 12 API 变更（中优先级）
+
+1. `App.axaml.cs`: 替换 `BindingPlugins.DataValidators` 的访问方式
+2. `DesktopComponentFailureView.cs`: 使用新的剪贴板 API
+3. `MonetColorService.cs`: 更新 `Bitmap.CopyPixels` 调用签名
+
+### Phase 4: 修复第三方库变更（中优先级）
+
+1. `SettingsWindow.axaml.cs`: 替换 `FluentIcons.Avalonia.SymbolIconSource` 为 v3 等效 API
+
+### Phase 5: 清理过时属性（低优先级）
+
+1. 批量替换 `Watermark` → `PlaceholderText`（所有 .cs 和 .axaml）
+
+## 验证步骤
+
+* 每阶段修复后运行 `dotnet build LanMountainDesktop.slnx -c Debug`
+
+* 最终运行 `dotnet test LanMountainDesktop.slnx -c Debug`
+