Show folder names immediately and refresh stale index sizes without walking the whole drive.

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

src/Explorer.Contracts/IWorkbenchHost.cs

@@ -16,6 +16,8 @@ public interface IIndexingHost
     void EnqueueFullScan(long sourceId);
     void EnqueueFolderScan(long sourceId, string pathRel);
     void EnqueueReconcile(long sourceId, string pathRel);
+    /// <summary>Shallow reconcile, then descend into child folders whose index no longer matches disk.</summary>
+    void EnqueueVerify(long sourceId, string pathRel) => EnqueueReconcile(sourceId, pathRel);
     void Cancel(long sourceId);
 }
 
@@ -63,6 +65,8 @@ public interface ISourceHost
     Task<Source> AddUncAsync(string path, CancellationToken cancellationToken = default);
     Task<Source?> EnsureForPathAsync(string path, CancellationToken cancellationToken = default);
     Task<bool> ForgetAsync(string path, CancellationToken cancellationToken = default);
+    Task<Source?> MarkReachableAsync(string path, CancellationToken cancellationToken = default)
+        => Task.FromResult<Source?>(null);
 }
 
 public interface IIndexMutations