Profile editor - Fix undoing profile editor commands

- Undoing a change to an existing keyframe's value restores the value instead of deleting the keyframe
- Undoing "remove effect" puts the effect back in its place instead of below the next one
- Undoing "toggle keyframes" restores what it was before
- Undoing a brush change on a layer that had no brush removes the brush again, using the new Layer.RemoveLayerBrush
- Undoing "add element" disables the element again
- Undoing an event path change back to no path goes back to an event start node, like a new condition
- MoveProfileElement says "Move folder" for folders
- UpdateLayerProperty without a time no longer calls itself "Add ... keyframe"

src/Artemis.UI.Shared.Tests/ProfileEditor/Commands/LayerBrushAndLedCommandTests.cs

@@ -67,7 +67,7 @@ public class LayerBrushAndLedCommandTests : ProfileEditorTestBase
     }
 
     [Fact]
-    public void ChangeLayerBrush_Undo_OnALayerWithoutBrush_KeepsTheNewBrush()
+    public void ChangeLayerBrush_Undo_OnALayerWithoutBrush_RemovesTheNewBrush()
     {
         Layer layer = new(Root, "Layer without brush");
         Root.AddChild(layer);
@@ -76,8 +76,8 @@ public class LayerBrushAndLedCommandTests : ProfileEditorTestBase
         command.Execute();
         command.Undo();
 
-        // Pinned as-is: with no brush to go back to, undo leaves the new brush (and the brush reference) in place
-        layer.LayerBrush.ShouldBeOfType<GradientTestBrush>();
+        layer.LayerBrush.ShouldBeNull();
+        layer.General.BrushReference.CurrentValue.ShouldBeNull();
     }
 
     [Fact]