Add autohide option to Island Mode

### Feature Description

Add an option to autohide the Island.
The Island could appear when hovering the top off the screen like standard bars.

### Use Case

This feature will allow people to take full advantage of the screen space (not having lost space at the top for the island, or the island hovering windows) while using the Island mode offering a compact view to interact with the shell.

### Compositor(s)

All compositors

### If Other, please specify

_No response_

### Proposed Solution

Add an option in settings to auhide the Island like it is done for standard bars.

### Alternatives/Existing Solutions

_No response_

Start by locating the Island Mode settings and the existing autohide behavior for standard bars. Trace how hover detection and compositor-specific shell behavior are handled, then verify that the new setting makes the Island appear when hovering at the top across all supported compositors.

Written by the indexing model from the issue text.