feat(installer): rewrite WelcomePage for download-mode + update heading

Removes SourceDirectory field (no longer in InstallContext), adds
dynamic Heading/Subheading/InstallDirEditable for FreshInstall vs Update
mode, and updates XAML to match sibling page style.

src/ClaudeDo.Installer/Pages/WelcomePage/WelcomePageView.xaml

@@ -9,40 +9,29 @@
 
     <ScrollViewer VerticalScrollBarVisibility="Auto">
         <StackPanel MaxWidth="520">
-            <TextBlock Text="Welcome to ClaudeDo Setup" FontSize="20" FontWeight="SemiBold"
-                       Margin="0,0,0,6"/>
-            <TextBlock Text="This wizard will build, configure, and install ClaudeDo on your machine."
-                       Foreground="{StaticResource TextSecondaryBrush}" Margin="0,0,0,24"
-                       TextWrapping="Wrap"/>
 
-            <!-- Source Directory -->
+            <TextBlock Text="{Binding Heading}" FontSize="20" FontWeight="SemiBold" Margin="0,0,0,6"/>
-            <Label Content="Source Directory"/>
+            <TextBlock Text="{Binding Subheading}" TextWrapping="Wrap"
-            <Grid Margin="0,0,0,4">
+                       Foreground="{StaticResource TextSecondaryBrush}" Margin="0,0,0,24"/>
-                <Grid.ColumnDefinitions>
-                    <ColumnDefinition Width="*"/>
-                    <ColumnDefinition Width="Auto"/>
-                </Grid.ColumnDefinitions>
-                <TextBox Grid.Column="0" Text="{Binding SourceDirectory, UpdateSourceTrigger=PropertyChanged}"/>
-                <Button Grid.Column="1" Content="Browse..." Command="{Binding BrowseSourceCommand}"
-                        Margin="8,0,0,0"/>
-            </Grid>
-            <TextBlock Text="{Binding SourceError}" Foreground="{StaticResource ErrorBrush}" FontSize="11"
-                       Visibility="{Binding SourceError, Converter={StaticResource NullToCollapsedConverter}}"
-                       Margin="0,0,0,16"/>
 
-            <!-- Install Directory -->
             <Label Content="Install Directory"/>
             <Grid Margin="0,0,0,4">
                 <Grid.ColumnDefinitions>
                     <ColumnDefinition Width="*"/>
                     <ColumnDefinition Width="Auto"/>
                 </Grid.ColumnDefinitions>
-                <TextBox Grid.Column="0" Text="{Binding InstallDirectory, UpdateSourceTrigger=PropertyChanged}"/>
+                <TextBox Grid.Column="0"
-                <Button Grid.Column="1" Content="Browse..." Command="{Binding BrowseInstallCommand}"
+                         Text="{Binding InstallDirectory, UpdateSourceTrigger=PropertyChanged}"
-                        Margin="8,0,0,0"/>
+                         IsEnabled="{Binding InstallDirEditable}"/>
+                <Button Grid.Column="1"
+                        Content="Browse..."
+                        Margin="8,0,0,0"
+                        Command="{Binding BrowseInstallCommand}"
+                        IsEnabled="{Binding InstallDirEditable}"/>
             </Grid>
             <TextBlock Text="{Binding InstallError}" Foreground="{StaticResource ErrorBrush}" FontSize="11"
                        Visibility="{Binding InstallError, Converter={StaticResource NullToCollapsedConverter}}"/>
+
         </StackPanel>
     </ScrollViewer>
 </UserControl>

src/ClaudeDo.Installer/Pages/WelcomePage/WelcomePageViewModel.cs

@@ -19,88 +19,64 @@ public partial class WelcomePageViewModel : ObservableObject, IInstallerPage
     public bool ShowInSettings => false;
     public UserControl View => _view ??= new WelcomePageView { DataContext = this };
 
-    [ObservableProperty] private string _sourceDirectory = "";
     [ObservableProperty] private string _installDirectory = @"C:\Program Files\ClaudeDo";
-    [ObservableProperty] private string? _sourceError;
     [ObservableProperty] private string? _installError;
+    [ObservableProperty] private string _heading = "Install ClaudeDo";
+    [ObservableProperty] private string _subheading = "Set the installation directory and continue.";
+    [ObservableProperty] private bool _installDirEditable = true;
 
     public WelcomePageViewModel(InstallContext context)
     {
         _context = context;
-        _sourceDirectory = DetectSourceDirectory();
     }
 
     public Task LoadAsync()
     {
-        if (!string.IsNullOrEmpty(_context.SourceDirectory))
+        InstallDirectory = string.IsNullOrEmpty(_context.InstallDirectory)
-            SourceDirectory = _context.SourceDirectory;
+            ? @"C:\Program Files\ClaudeDo"
-        if (!string.IsNullOrEmpty(_context.InstallDirectory))
+            : _context.InstallDirectory;
-            InstallDirectory = _context.InstallDirectory;
+
+        switch (_context.Mode)
+        {
+            case InstallerMode.FreshInstall:
+                Heading = "Install ClaudeDo";
+                Subheading = "Choose where to install ClaudeDo, then click Next.";
+                InstallDirEditable = true;
+                break;
+
+            case InstallerMode.Update:
+                Heading = $"Update ClaudeDo  {_context.InstalledVersion}  ->  {_context.LatestVersion}";
+                Subheading = "Your tasks, config, and database will be preserved. Click Next to continue.";
+                InstallDirEditable = false;
+                break;
+        }
+
         return Task.CompletedTask;
     }
 
     public Task ApplyAsync()
     {
-        _context.SourceDirectory = SourceDirectory;
         _context.InstallDirectory = InstallDirectory;
         return Task.CompletedTask;
     }
 
     public bool Validate()
     {
-        var valid = true;
-
-        if (string.IsNullOrWhiteSpace(SourceDirectory) ||
-            !File.Exists(Path.Combine(SourceDirectory, "ClaudeDo.slnx")))
-        {
-            SourceError = "Source directory must contain ClaudeDo.slnx";
-            valid = false;
-        }
-        else
-        {
-            SourceError = null;
-        }
-
         if (string.IsNullOrWhiteSpace(InstallDirectory))
         {
             InstallError = "Install directory is required";
-            valid = false;
+            return false;
         }
-        else
-        {
         InstallError = null;
-        }
+        return true;
-
-        return valid;
-    }
-
-    [RelayCommand]
-    private void BrowseSource()
-    {
-        var dialog = new OpenFolderDialog { Title = "Select ClaudeDo source directory" };
-        if (dialog.ShowDialog() == true)
-            SourceDirectory = dialog.FolderName;
     }
 
     [RelayCommand]
     private void BrowseInstall()
     {
+        if (!InstallDirEditable) return;
         var dialog = new OpenFolderDialog { Title = "Select installation directory" };
         if (dialog.ShowDialog() == true)
             InstallDirectory = dialog.FolderName;
     }
-
-    private static string DetectSourceDirectory()
-    {
-        var dir = AppContext.BaseDirectory;
-        for (var i = 0; i < 8; i++)
-        {
-            if (File.Exists(Path.Combine(dir, "ClaudeDo.slnx")))
-                return dir;
-            var parent = Directory.GetParent(dir)?.FullName;
-            if (parent is null) break;
-            dir = parent;
-        }
-        return "";
-    }
 }