feat(diff): add persisted side-by-side and wrap toggles to the diff viewer

src/ClaudeDo.Ui/ViewModels/Modals/DiffViewerViewModel.cs

@@ -1,7 +1,10 @@
+using System;
 using System.Collections.ObjectModel;
+using System.IO;
 using CommunityToolkit.Mvvm.ComponentModel;
 using CommunityToolkit.Mvvm.Input;
 using ClaudeDo.Data.Git;
+using ClaudeDo.Ui;
 using ClaudeDo.Ui.Localization;
 using ClaudeDo.Ui.Services;
 
@@ -21,6 +24,7 @@ public sealed partial class DiffViewerViewModel : ViewModelBase
 {
     private readonly GitService _git;
     private readonly IWorkerClient _worker;
+    private readonly AppSettings _settings;
 
     [ObservableProperty]
     [NotifyPropertyChangedFor(nameof(IsPlanning))]
@@ -56,6 +60,31 @@ public sealed partial class DiffViewerViewModel : ViewModelBase
     [ObservableProperty] private string _displayedDiff = "";
     [ObservableProperty] private string? _statusMessage;
 
+    // ── View toggles (persisted to ui.config.json) ──────────────────────────
+    [ObservableProperty] private bool _isSplitView;
+    [ObservableProperty] private bool _wrapLines;
+
+    partial void OnIsSplitViewChanged(bool value)
+    {
+        _settings.DiffViewMode = value ? "split" : "unified";
+        PersistViewPreferences();
+    }
+
+    partial void OnWrapLinesChanged(bool value)
+    {
+        _settings.DiffWrapLines = value;
+        PersistViewPreferences();
+    }
+
+    /// A failed preference write must never take the diff viewer down with it; the toggle
+    /// still works for this session, it just won't survive a restart.
+    private void PersistViewPreferences()
+    {
+        try { _settings.Save(); }
+        catch (IOException) { }
+        catch (UnauthorizedAccessException) { }
+    }
+
     // ── Planning combined toggle ────────────────────────────────────────────
     [ObservableProperty] private bool _isCombinedMode;
     [ObservableProperty] private string? _combinedWarning;
@@ -63,10 +92,13 @@ public sealed partial class DiffViewerViewModel : ViewModelBase
 
     public Action? CloseAction { get; set; }
 
-    public DiffViewerViewModel(GitService git, IWorkerClient worker)
+    public DiffViewerViewModel(GitService git, IWorkerClient worker, AppSettings settings)
     {
         _git = git;
         _worker = worker;
+        _settings = settings;
+        _isSplitView = string.Equals(settings.DiffViewMode, "split", StringComparison.OrdinalIgnoreCase);
+        _wrapLines = settings.DiffWrapLines;
     }
 
     [RelayCommand]