Add OOBE startup presentation and settings merge

Introduce a new OOBE step for "Startup & Presentation" that exposes startup and UI preferences in OobeWindow (toggles for taskbar, slide/fade transitions, fused popup, and autostart). Add HostAppSettingsOobeMerger to read/write Host settings.json (PascalCase fields) and MergeStartupPresentation behavior, plus LauncherWindowsStartupService to sync the current Launcher into the Windows Run key on Windows. Wire UI handlers, persist choices on Next, and load defaults when entering the step. Include unit tests for the merger, adjust SettingsWindow navigation pane/toggle handling, and update docs/LAUNCHER.md to describe the new OOBE step and implementation files.

LanMountainDesktop.Launcher/Views/OobeWindow.axaml

@@ -596,7 +596,142 @@
       </StackPanel>
     </Grid>
 
-    <!-- 步骤 4: 信息与隐私页面 -->
+    <!-- 步骤 4: 启动与展示（紧接数据保存位置） -->
+    <Grid x:Name="StartupPresentationStep" Margin="48" RowDefinitions="Auto,*,Auto" IsVisible="False">
+      <StackPanel Grid.Row="0" Spacing="8" Margin="0,0,0,16">
+        <TextBlock Text="启动与展示"
+                   FontSize="24"
+                   FontWeight="SemiBold"
+                   Foreground="{DynamicResource TextFillColorPrimaryBrush}" />
+        <TextBlock Text="这些选项可随时在桌面应用的「设置」中更改。主窗口滑动入场仅在 Windows 上可用。"
+                   FontSize="13"
+                   TextWrapping="Wrap"
+                   Foreground="{DynamicResource TextFillColorSecondaryBrush}" />
+      </StackPanel>
+
+      <ScrollViewer Grid.Row="1" VerticalScrollBarVisibility="Auto">
+        <StackPanel Spacing="14">
+          <Border Background="{DynamicResource CardBackgroundFillColorDefaultBrush}"
+                  CornerRadius="{DynamicResource DesignCornerRadiusMd}"
+                  Padding="16">
+            <Grid ColumnDefinitions="*,Auto">
+              <StackPanel Grid.Column="0" Spacing="4">
+                <TextBlock Text="在任务栏显示主桌面窗口"
+                           FontSize="14"
+                           FontWeight="SemiBold"
+                           Foreground="{DynamicResource TextFillColorPrimaryBrush}" />
+                <TextBlock Text="开启后最小化时可在任务栏保留条目；关闭则更多依赖托盘图标。"
+                           FontSize="12"
+                           TextWrapping="Wrap"
+                           Foreground="{DynamicResource TextFillColorSecondaryBrush}" />
+              </StackPanel>
+              <ToggleSwitch x:Name="OobeShowInTaskbarToggle"
+                            Grid.Column="1"
+                            VerticalAlignment="Center" />
+            </Grid>
+          </Border>
+
+          <Border x:Name="OobeSlideTransitionSection"
+                  Background="{DynamicResource CardBackgroundFillColorDefaultBrush}"
+                  CornerRadius="{DynamicResource DesignCornerRadiusMd}"
+                  Padding="16">
+            <StackPanel Spacing="12">
+              <Grid ColumnDefinitions="*,Auto">
+                <StackPanel Grid.Column="0" Spacing="4">
+                  <TextBlock Text="以滑动方式显示主窗口"
+                             FontSize="14"
+                             FontWeight="SemiBold"
+                             Foreground="{DynamicResource TextFillColorPrimaryBrush}" />
+                  <TextBlock Text="自屏幕边缘滑入；与「淡入」二选一。"
+                             FontSize="12"
+                             TextWrapping="Wrap"
+                             Foreground="{DynamicResource TextFillColorSecondaryBrush}" />
+                </StackPanel>
+                <ToggleSwitch x:Name="OobeSlideTransitionToggle"
+                              Grid.Column="1"
+                              VerticalAlignment="Center" />
+              </Grid>
+              <Grid ColumnDefinitions="*,Auto">
+                <StackPanel Grid.Column="0" Spacing="4">
+                  <TextBlock Text="启动时使用淡入过渡"
+                             FontSize="14"
+                             FontWeight="SemiBold"
+                             Foreground="{DynamicResource TextFillColorPrimaryBrush}" />
+                  <TextBlock Text="在未启用滑动入场时建议使用。"
+                             FontSize="12"
+                             TextWrapping="Wrap"
+                             Foreground="{DynamicResource TextFillColorSecondaryBrush}" />
+                </StackPanel>
+                <ToggleSwitch x:Name="OobeFadeTransitionToggle"
+                              Grid.Column="1"
+                              VerticalAlignment="Center" />
+              </Grid>
+            </StackPanel>
+          </Border>
+
+          <Border Background="{DynamicResource CardBackgroundFillColorDefaultBrush}"
+                  CornerRadius="{DynamicResource DesignCornerRadiusMd}"
+                  Padding="16">
+            <Grid ColumnDefinitions="*,Auto">
+              <StackPanel Grid.Column="0" Spacing="4">
+                <StackPanel Orientation="Horizontal" Spacing="8">
+                  <fi:SymbolIcon Symbol="SlideLayout"
+                                 FontSize="20"
+                                 Foreground="{DynamicResource AccentFillColorDefaultBrush}" />
+                  <TextBlock Text="融合桌面与弹入手势"
+                             FontSize="14"
+                             FontWeight="SemiBold"
+                             Foreground="{DynamicResource TextFillColorPrimaryBrush}" />
+                </StackPanel>
+                <TextBlock Text="同时启用融合桌面与三指滑动手势，以便使用边缘弹入与相关实验特性（与设置中开发者选项一致）。"
+                           FontSize="12"
+                           TextWrapping="Wrap"
+                           Foreground="{DynamicResource TextFillColorSecondaryBrush}" />
+              </StackPanel>
+              <ToggleSwitch x:Name="OobeFusedPopupToggle"
+                            Grid.Column="1"
+                            VerticalAlignment="Center" />
+            </Grid>
+          </Border>
+
+          <Border Background="{DynamicResource CardBackgroundFillColorDefaultBrush}"
+                  CornerRadius="{DynamicResource DesignCornerRadiusMd}"
+                  Padding="16">
+            <Grid ColumnDefinitions="*,Auto">
+              <StackPanel Grid.Column="0" Spacing="4">
+                <TextBlock Text="登录 Windows 时自动启动阑山桌面"
+                           FontSize="14"
+                           FontWeight="SemiBold"
+                           Foreground="{DynamicResource TextFillColorPrimaryBrush}" />
+                <TextBlock x:Name="OobeAutoStartDescriptionText"
+                           Text="通过当前用户的启动项注册本启动器（与安装程序可选任务使用同一注册表项）。"
+                           FontSize="12"
+                           TextWrapping="Wrap"
+                           Foreground="{DynamicResource TextFillColorSecondaryBrush}" />
+              </StackPanel>
+              <ToggleSwitch x:Name="OobeAutoStartToggle"
+                            Grid.Column="1"
+                            VerticalAlignment="Center" />
+            </Grid>
+          </Border>
+        </StackPanel>
+      </ScrollViewer>
+
+      <StackPanel Grid.Row="2"
+                  Orientation="Horizontal"
+                  HorizontalAlignment="Right"
+                  Spacing="12"
+                  Margin="0,24,0,0">
+        <Button x:Name="StartupPresentationBackButton"
+                Content="返回"
+                Theme="{DynamicResource ButtonTheme}" />
+        <Button x:Name="StartupPresentationNextButton"
+                Content="下一步"
+                Theme="{DynamicResource AccentButtonTheme}" />
+      </StackPanel>
+    </Grid>
+
+    <!-- 步骤 5: 信息与隐私页面 -->
     <Grid x:Name="PrivacyStep" Margin="48" RowDefinitions="Auto,*,Auto" IsVisible="False">
       <StackPanel Grid.Row="0" Spacing="8" Margin="0,0,0,24">
         <TextBlock Text="信息与隐私"
@@ -731,7 +866,7 @@
       </StackPanel>
     </Grid>
 
-    <!-- 步骤 5: 欢迎完成页面 -->
+    <!-- 步骤 6: 欢迎完成页面 -->
     <Grid x:Name="WelcomeStep" Margin="48" RowDefinitions="*,Auto" IsVisible="False">
       <StackPanel Grid.Row="0"
                   VerticalAlignment="Center"