TreeItemLayout: Umounts actions between mouse events

The actions slot in the TreeItemLayout is unmounted between mouse events. This can cause components like Menus to appear to close when the mouse leaves the actions boundary

![actions](https://github.com/user-attachments/assets/8d6eee60-d5ce-42d4-a8c3-aa87bbf50314)
