Always on top: Automatic hiding of windows when they are docked to the edge.

### Description of the new feature / enhancement

- After the window is docked to the edge, it automatically enters a hidden state, leaving only a thin edge as the trigger area, and the window does not seize the focus.

- When the mouse moves to the trigger area at the corresponding edge of the screen, the hidden window smoothly pops up and is fully displayed.

- After the mouse leaves the window area, the window delays for a short period of time and then automatically retracts and hides again.

### Scenario when this would be used?

Used to reduce screen obstruction when making desktop reminders

### Supporting information

_No response_

The issue does not name files, tests, or entry points, so begin by locating the window-docking implementation and its existing edge-trigger behavior. Done means docked windows retract without taking focus, reveal smoothly when the trigger edge is reached, and hide again after the pointer leaves and a short delay expires.

Written by the indexing model from the issue text.