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>

src/Explorer.Presentation/ViewModels/DuplicateViewModel.cs

@@ -0,0 +1,79 @@
+using System.Collections.ObjectModel;
+using CommunityToolkit.Mvvm.ComponentModel;
+using CommunityToolkit.Mvvm.Input;
+using Explorer.Application;
+using Explorer.Domain;
+using Explorer.Domain.Abstractions;
+
+namespace Explorer.Presentation.ViewModels;
+
+public sealed partial class DuplicateViewModel : ObservableObject
+{
+    private readonly IIndexStore _store;
+    private readonly SourceManager _sources;
+
+    [ObservableProperty] private bool _isOpen;
+    [ObservableProperty] private bool _isBusy;
+    [ObservableProperty] private string _status = "";
+
+    public DuplicateViewModel(IIndexStore store, SourceManager sources)
+    {
+        _store = store;
+        _sources = sources;
+        Groups = [];
+    }
+
+    public ObservableCollection<string> Groups { get; }
+
+    [RelayCommand]
+    public async Task OpenAsync()
+    {
+        IsOpen = true;
+        IsBusy = true;
+        Status = "Finding size collisions…";
+        Groups.Clear();
+        try
+        {
+            var lines = await Task.Run(async () =>
+            {
+                await _store.Hashes.EnqueueSizeCollisionsAsync(null).ConfigureAwait(false);
+                var groups = await _store.Hashes.GetDuplicateGroupsAsync(null, null, 200).ConfigureAwait(false);
+                var sources = (await _sources.RefreshOnlineStateAsync().ConfigureAwait(false)).ToDictionary(s => s.Id);
+                var result = new List<string>();
+                foreach (var g in groups)
+                {
+                    if (g.SameFileId)
+                    {
+                        continue;
+                    }
+
+                    var paths = string.Join(" | ", g.Entries.Select(e =>
+                    {
+                        sources.TryGetValue(e.SourceId, out var s);
+                        return PathRules.Combine(s?.LastRootPath ?? s?.DisplayName ?? "", e.PathRel);
+                    }));
+                    result.Add($"{Formatters.Size(g.SizeBytes)} · {g.Entries.Count} files · {paths}");
+                }
+
+                return result;
+            }).ConfigureAwait(true);
+
+            foreach (var line in lines)
+            {
+                Groups.Add(line);
+            }
+
+            Status = Groups.Count == 0
+                ? "No confirmed duplicates yet. Hashing continues in the background."
+                : $"{Groups.Count} duplicate groups";
+        }
+        catch (Exception)
+        {
+            Status = "Could not load duplicates.";
+        }
+        finally
+        {
+            IsBusy = false;
+        }
+    }
+}