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.Analysis/AnalysisResultCache.cs

@@ -0,0 +1,45 @@
+namespace Explorer.Analysis;
+
+internal sealed class AnalysisResultCache
+{
+    private const int MaxEntries = 32;
+    private static readonly TimeSpan Ttl = TimeSpan.FromSeconds(20);
+
+    private readonly object _gate = new();
+    private readonly Dictionary<string, Entry> _items = new(StringComparer.Ordinal);
+
+    public bool TryGet<T>(string key, long stamp, out T value)
+    {
+        lock (_gate)
+        {
+            if (_items.TryGetValue(key, out var entry)
+                && entry.Stamp == stamp
+                && entry.Utc + Ttl > DateTime.UtcNow
+                && entry.Value is T typed)
+            {
+                value = typed;
+                return true;
+            }
+        }
+
+        value = default!;
+        return false;
+    }
+
+    public void Set<T>(string key, long stamp, T value)
+    {
+        lock (_gate)
+        {
+            _items[key] = new Entry(stamp, value!, DateTime.UtcNow);
+            if (_items.Count <= MaxEntries)
+            {
+                return;
+            }
+
+            var oldest = _items.OrderBy(p => p.Value.Utc).First().Key;
+            _items.Remove(oldest);
+        }
+    }
+
+    private readonly record struct Entry(long Stamp, object Value, DateTime Utc);
+}