Tidy gallery installer review follow-ups

Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>

Copilot-Session: b34be394-240f-4bdd-878f-41460bc09c36

src/modules/cmdpal/Microsoft.CmdPal.UI.ViewModels/Services/JsonRpcExtensionService.cs

@@ -327,10 +327,9 @@ public sealed partial class JsonRpcExtensionService : IExtensionService, IJsExte
             return [];
         }
 
-        // Start the watcher before scanning so a package installed while the scan runs
-        // is still observed (the per-directory gate and the already-loaded check make a
-        // watcher-driven load and a scan-driven load for the same directory idempotent).
         RecoverStaleGalleryInstallMarkersOnce();
+
+        // Start the watcher before scanning so installs during the scan are still observed.
         StartDirectoryWatcher();
 
         var accepted = DiscoverAcceptedManifests(ExtensionsPath);

src/modules/cmdpal/Microsoft.CmdPal.UI.ViewModels/Services/NpmCommandRunner.cs

@@ -549,9 +549,14 @@ public sealed class NpmCommandRunner : INpmCommandRunner
             return true;
         }
 
-        return exception is AggregateException aggregateException
-            && aggregateException.Flatten().InnerExceptions.Count > 0
-            && aggregateException.Flatten().InnerExceptions.All(IsExpectedTerminationException);
+        if (exception is not AggregateException aggregateException)
+        {
+            return false;
+        }
+
+        var flattenedException = aggregateException.Flatten();
+        return flattenedException.InnerExceptions.Count > 0
+            && flattenedException.InnerExceptions.All(IsExpectedTerminationException);
     }
 
     private static bool IsReparsePoint(string path)