feat(installer): add WPF installer/configurator project

Standalone WPF app (ClaudeDo.Installer) that handles full installation
and ongoing configuration of ClaudeDo. Two modes: wizard for first run,
tabbed settings panel for subsequent launches. Page-based extensibility
via IInstallerPage interface — adding new config sections requires only
one new class.

Install pipeline: dotnet publish, deploy binaries, write configs, init
DB (via SchemaInitializer from ClaudeDo.Data), register Windows Service,
create shortcuts. Dark theme matching the Avalonia app (forest teal accent).

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/ClaudeDo.Installer/Views/SettingsViewModel.cs

@@ -0,0 +1,87 @@
+using System.Windows;
+using ClaudeDo.Installer.Core;
+using CommunityToolkit.Mvvm.ComponentModel;
+using CommunityToolkit.Mvvm.Input;
+
+namespace ClaudeDo.Installer.Views;
+
+public partial class SettingsViewModel : ObservableObject
+{
+    private readonly InstallContext _context;
+
+    public IReadOnlyList<IInstallerPage> Pages { get; }
+
+    [ObservableProperty]
+    private IInstallerPage? _selectedPage;
+
+    [ObservableProperty]
+    private string? _statusMessage;
+
+    [ObservableProperty]
+    private bool _isStatusError;
+
+    public SettingsViewModel(PageResolver resolver, InstallContext context)
+    {
+        Pages = resolver.SettingsPages;
+        _context = context;
+        _selectedPage = Pages.FirstOrDefault();
+
+        _ = LoadAllAsync();
+    }
+
+    private async Task LoadAllAsync()
+    {
+        foreach (var page in Pages)
+            await page.LoadAsync();
+    }
+
+    [RelayCommand]
+    private async Task Apply()
+    {
+        // Validate all pages
+        foreach (var page in Pages)
+        {
+            if (!page.Validate())
+            {
+                SelectedPage = page;
+                StatusMessage = $"Validation failed on {page.Title}. Please fix the errors.";
+                IsStatusError = true;
+                return;
+            }
+        }
+
+        // Apply all pages (writes to InstallContext)
+        foreach (var page in Pages)
+            await page.ApplyAsync();
+
+        // Write config files directly
+        var workerCfg = new InstallerWorkerConfig
+        {
+            DbPath = _context.DbPath,
+            SandboxRoot = _context.SandboxRoot,
+            LogRoot = _context.LogRoot,
+            WorktreeRootStrategy = _context.WorktreeRootStrategy,
+            CentralWorktreeRoot = _context.CentralWorktreeRoot,
+            QueueBackstopIntervalMs = _context.QueueBackstopIntervalMs,
+            SignalRPort = _context.SignalRPort,
+            ClaudeBin = _context.ClaudeBin,
+        };
+        workerCfg.Save();
+
+        var uiCfg = new InstallerAppSettings
+        {
+            DbPath = _context.UiDbPath,
+            SignalRUrl = _context.SignalRUrl,
+        };
+        uiCfg.Save();
+
+        StatusMessage = "Settings saved successfully.";
+        IsStatusError = false;
+    }
+
+    [RelayCommand]
+    private void Close()
+    {
+        Application.Current.Shutdown();
+    }
+}