Add host activity and DB browser, and keep dialogs, drag-drop, and idle maintenance responsive.

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

tests/Explorer.Domain.Tests/DomainTests.cs

@@ -299,6 +299,25 @@ public class DragDropPolicyTests
         Assert.False(DragDropPolicy.IsInvalidTarget([@"C:\Docs"], @"D:\Other"));
     }
 
+    [Fact]
+    public void Click_jitter_does_not_start_a_drag()
+    {
+        Assert.False(DragDropPolicy.ExceedsDistance(4, 3, DragDropPolicy.DragStartDistance));
+        Assert.False(DragDropPolicy.ExceedsDistance(12, 8, DragDropPolicy.DragStartDistance));
+        Assert.True(DragDropPolicy.ExceedsDistance(16, 0, DragDropPolicy.DragStartDistance));
+        Assert.True(DragDropPolicy.ExceedsDistance(12, 12, DragDropPolicy.DragStartDistance));
+    }
+
+    [Fact]
+    public void Same_folder_drop_is_redundant()
+    {
+        Assert.True(DragDropPolicy.AllAlreadyInDirectory([@"C:\Docs\a.txt", @"C:\Docs\b.txt"], @"C:\Docs"));
+        Assert.True(DragDropPolicy.AllAlreadyInDirectory([@"C:\Docs\a.txt"], @"C:\Docs\"));
+        Assert.False(DragDropPolicy.AllAlreadyInDirectory([@"C:\Docs\a.txt"], @"C:\Other"));
+        Assert.False(DragDropPolicy.AllAlreadyInDirectory([@"C:\Docs\a.txt", @"C:\Other\b.txt"], @"C:\Docs"));
+        Assert.False(DragDropPolicy.AllAlreadyInDirectory([], @"C:\Docs"));
+    }
+
     [Fact]
     public void Same_volume_uses_drive_or_unc_share()
     {