Make drag-and-drop follow Windows Explorer and refresh the tree after folder operations.

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

tests/Explorer.Domain.Tests/DomainTests.cs

@@ -43,6 +43,8 @@ public class PathRulesTests
         Assert.Equal(@"Windows\System32", PathRules.MakeRelative(@"C:\", @"C:\Windows\System32"));
         Assert.Equal(@"C:\Windows", PathRules.Parent(@"C:\Windows\System32"));
         Assert.Equal(@"C:\", PathRules.Parent(@"C:\Windows"));
+        Assert.True(PathRules.DriveLetterSortKey(@"D:\") < PathRules.DriveLetterSortKey(@"F:\"));
+        Assert.True(PathRules.DriveLetterSortKey(@"C:\") < PathRules.DriveLetterSortKey(@"\\media\movies"));
         Assert.Equal(@"pack.zip\docs", PathRules.RelativeParent(@"pack.zip\docs\a.txt"));
         Assert.Equal("pack.zip", PathRules.RelativeParent(@"pack.zip\docs"));
         Assert.Equal("", PathRules.RelativeParent("pack.zip"));
@@ -140,6 +142,56 @@ public class VolumeIdentityTests
     }
 }
 
+public class LocationClassifierTests
+{
+    [Fact]
+    public void Classifies_known_protected_locations()
+    {
+        var svi = LocationClassifier.Classify(
+            @"C:\System Volume Information", "System Volume Information",
+            AttributeFlags.Directory | AttributeFlags.Hidden | AttributeFlags.System, true);
+        Assert.True(svi.IsProtected);
+        Assert.True(svi.IsHidden);
+        Assert.True(svi.IsSystem);
+        Assert.False(svi.IsRecycleBin);
+
+        var recycle = LocationClassifier.Classify(
+            @"D:\$RECYCLE.BIN", "$RECYCLE.BIN",
+            AttributeFlags.Directory | AttributeFlags.Hidden | AttributeFlags.System, true);
+        Assert.True(recycle.IsProtected);
+        Assert.True(recycle.IsRecycleBin);
+
+        var pagefile = LocationClassifier.Classify(
+            @"C:\pagefile.sys", "pagefile.sys", AttributeFlags.Hidden | AttributeFlags.System, false);
+        Assert.True(pagefile.IsProtected);
+        Assert.False(pagefile.IsRecycleBin);
+    }
+
+    [Fact]
+    public void Does_not_treat_normal_hidden_user_files_as_protected()
+    {
+        var desktopIni = LocationClassifier.Classify(
+            @"C:\Users\Ada\Desktop\desktop.ini", "desktop.ini",
+            AttributeFlags.Hidden | AttributeFlags.System, false);
+        Assert.True(desktopIni.IsHidden);
+        Assert.True(desktopIni.IsSystem);
+        Assert.False(desktopIni.IsProtected);
+
+        var movies = LocationClassifier.Classify(
+            @"C:\Movies", "Movies", AttributeFlags.Directory, true);
+        Assert.False(movies.IsProtected);
+        Assert.False(movies.IsHidden);
+    }
+
+    [Fact]
+    public void Access_denied_marks_protected()
+    {
+        var info = LocationClassifier.Classify(@"C:\locked", "locked", AttributeFlags.Directory, true, accessDenied: true);
+        Assert.True(info.AccessDenied);
+        Assert.True(info.IsProtected);
+    }
+}
+
 public class ExcludeEvaluatorTests
 {
     [Fact]
@@ -182,3 +234,36 @@ public class ReparsePolicyTests
         Assert.False(ReparsePolicy.ShouldRecurseIntoDirectory(item));
     }
 }
+
+public class DragDropPolicyTests
+{
+    [Fact]
+    public void Modifiers_match_windows_explorer()
+    {
+        Assert.Equal(DropAction.Move, DragDropPolicy.Resolve(false, false, false, sameVolume: true));
+        Assert.Equal(DropAction.Copy, DragDropPolicy.Resolve(false, false, false, sameVolume: false));
+        Assert.Equal(DropAction.Copy, DragDropPolicy.Resolve(control: true, shift: false, alt: false, sameVolume: true));
+        Assert.Equal(DropAction.Move, DragDropPolicy.Resolve(control: false, shift: true, alt: false, sameVolume: false));
+        Assert.Equal(DropAction.Link, DragDropPolicy.Resolve(control: false, shift: false, alt: true, sameVolume: true));
+        Assert.Equal(DropAction.Link, DragDropPolicy.Resolve(control: true, shift: true, alt: false, sameVolume: false));
+    }
+
+    [Fact]
+    public void Rejects_virtual_and_self_targets()
+    {
+        Assert.True(DragDropPolicy.IsInvalidTarget([@"C:\Docs"], LocationRoots.ThisPc));
+        Assert.True(DragDropPolicy.IsInvalidTarget([@"C:\Docs"], @"C:\Docs"));
+        Assert.True(DragDropPolicy.IsInvalidTarget([@"C:\Docs"], @"C:\Docs\sub"));
+        Assert.False(DragDropPolicy.IsInvalidTarget([@"C:\Docs\file.txt"], @"C:\Docs"));
+        Assert.False(DragDropPolicy.IsInvalidTarget([@"C:\Docs"], @"D:\Other"));
+    }
+
+    [Fact]
+    public void Same_volume_uses_drive_or_unc_share()
+    {
+        Assert.True(PathRules.IsSameVolume(@"C:\a", @"C:\b"));
+        Assert.False(PathRules.IsSameVolume(@"C:\a", @"D:\b"));
+        Assert.True(PathRules.IsSameVolume(@"\\media\movies\a", @"\\media\movies\b"));
+        Assert.False(PathRules.IsSameVolume(@"\\media\movies\a", @"\\media\tv\b"));
+    }
+}