feat(ui): add Restore default agents button to Settings modal

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

@@ -161,6 +161,32 @@ public sealed partial class SettingsModalViewModel : ViewModelBase
         finally { IsBusy = false; }
     }
 
+    [RelayCommand]
+    private async Task RestoreDefaultAgents()
+    {
+        IsBusy = true;
+        StatusMessage = "";
+        try
+        {
+            var result = await _worker.RestoreDefaultAgentsAsync();
+            if (result is null)
+                StatusMessage = "Worker offline.";
+            else if (result.Copied == 0 && result.Skipped == 0)
+                StatusMessage = "No default agents bundled.";
+            else if (result.Copied == 0)
+                StatusMessage = "All default agents already present.";
+            else
+                StatusMessage = $"Restored {result.Copied} default agent(s).";
+
+            await _worker.RefreshAgentsAsync();
+        }
+        catch (Exception ex)
+        {
+            StatusMessage = $"Restore failed: {ex.Message}";
+        }
+        finally { IsBusy = false; }
+    }
+
     [RelayCommand]
     private void OpenPath(string? path)
     {