Add Explorer Workbench with hierarchical, off-UI Storage analysis.

Storage queries run in the background with cancellation and covering indexes so switching views no longer freezes the UI.

Co-authored-by: Cursor <cursoragent@cursor.com>

tests/Explorer.FileOperations.Tests/FileOperationTests.cs

@@ -0,0 +1,44 @@
+using Explorer.Domain;
+using Explorer.Domain.Abstractions;
+using Explorer.FileOperations;
+
+namespace Explorer.FileOperations.Tests;
+
+public class FileOperationTests
+{
+    [Fact]
+    public void New_folder_and_rename_on_real_filesystem()
+    {
+        var root = Path.Combine(Path.GetTempPath(), "ew-ops", Guid.NewGuid().ToString("N"));
+        Directory.CreateDirectory(root);
+        try
+        {
+            var ops = new FileOperationService(null!, new StubShell(), new StubEnum());
+            var created = ops.NewFolder(root);
+            Assert.True(Directory.Exists(created));
+            ops.Rename(created, "Renamed");
+            Assert.True(Directory.Exists(Path.Combine(root, "Renamed")));
+        }
+        finally
+        {
+            try { Directory.Delete(root, true); } catch { /* ignore */ }
+        }
+    }
+}
+
+file sealed class StubEnum : IFileSystemEnumerator
+{
+    public IEnumerable<FileSystemItem> EnumerateChildren(string directoryPath) => [];
+    public IReadOnlyList<FileSystemItem> EnumerateChildrenSafe(string directoryPath, out string? error) { error = null; return []; }
+    public FileSystemItem? GetItem(string path) => null;
+}
+
+file sealed class StubShell : IShellFileOperations
+{
+    public void Open(string path) { }
+    public bool DeleteToRecycleBin(IReadOnlyList<string> paths, out string? error) { error = "n/a"; return false; }
+    public bool CopyFileWithProgress(string source, string destination, bool overwrite, IProgress<long>? progress, CancellationToken cancellationToken, out string? error)
+    { error = "n/a"; return false; }
+    public bool MoveFileWithProgress(string source, string destination, bool overwrite, IProgress<long>? progress, CancellationToken cancellationToken, out string? error)
+    { error = "n/a"; return false; }
+}