Remove empty directories after mod update file deletion (#250)

When mod updates remove files, their parent directories may be left behind as empty folders. This adds cleanup logic to walk up the directory tree and remove empty directories after each file deletion.

---------

Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: ManlyMarco <39247311+ManlyMarco@users.noreply.github.com>

Author: Copilot

src/KKManager.Updater/Data/UpdateItem.cs

@@ -1,5 +1,6 @@
 using System;
 using System.IO;
+using System.Linq;
 using System.Security;
 using System.Threading;
 using System.Threading.Tasks;
@@ -120,6 +121,23 @@ public async Task Update(Progress<double> progressCallback, CancellationToken ca
                         {
                             downloadTarget.MoveTo(TargetPath.FullName);
                         }
+                        else
+                        {
+                            // File was deleted without replacement, try to remove now-empty parent directories
+                            var gameDir = InstallDirectoryHelper.GameDirectory.FullName;
+                            var dir = TargetPath.Directory;
+                            while (dir != null && dir.Exists && !PathTools.PathsEqual(dir.FullName, gameDir))
+                            {
+                                try
+                                {
+                                    if (dir.EnumerateFileSystemInfos().Any()) break;
+                                    Console.WriteLine($"Removing empty directory: {dir.FullName}");
+                                    dir.Delete(false);
+                                }
+                                catch (Exception ex) { Console.WriteLine($"Failed to remove empty directory {dir.FullName}: {ex.Message}"); break; }
+                                dir = dir.Parent;
+                            }
+                        }
                     }
                 }
                 catch (IOException)