fix(installer): fall back to Config on detection timeout when install.json exists

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/ClaudeDo.Installer/App.xaml.cs

@@ -1,4 +1,3 @@
-using System.IO;
 using System.Net.Http;
 using System.Reflection;
 using System.Windows;
@@ -29,7 +28,13 @@ public partial class App : Application
 
         // Default install dir for detection — on upgrade we stay where we were.
         var detector = _services.GetRequiredService<InstallModeDetector>();
-        var cts = new CancellationTokenSource(TimeSpan.FromSeconds(5));
+        using var cts = new CancellationTokenSource(TimeSpan.FromSeconds(5));
+
+        // Read manifest up front so we can fall back to Config if the API times out
+        // on an existing install. If the API is slow, we do NOT want to drop an
+        // already-installed user into FreshInstall — that would risk overwriting them.
+        var existingManifest = InstallManifestStore.TryRead(context.InstallDirectory);
+
         DetectedState state;
         try
         {
@@ -37,7 +42,9 @@ public partial class App : Application
         }
         catch (OperationCanceledException)
         {
-            state = new DetectedState(InstallerMode.FreshInstall, null, null, null);
+            state = existingManifest is not null
+                ? new DetectedState(InstallerMode.Config, existingManifest, null, null)
+                : new DetectedState(InstallerMode.FreshInstall, null, null, null);
         }
 
         context.Mode = state.Mode;