Notification drag direction should be aligned with its position

### Feature Description

A notification popup's drag direction should be oriented based on its popup position.

### Use Case

Currently, notification popups can be click-dragged to the left or right direction in order to dismiss it.

But this can look awkward depending on your popup position setting.

For example: if you set your popup position to "Top Center", the notification popup will only be draggable towards empty space, instead of the edge of the screen. This breaks the physically intuitive design of the drag motion.

### Compositor(s)

All compositors

### If Other, please specify

_No response_

### Proposed Solution

The drag direction should be based on the popup position:

- Top Right -> Draggable to the right edge
- Top Left -> Draggable to the left edge
- Top Center -> Draggable to the top edge
- Bottom Center -> Draggable to the bottom edge
- Bottom Right -> Draggable to the right edge
- Bottom Left -> Draggable to the left edge

### Alternatives/Existing Solutions

_No response_

Start by locating the notification popup's drag-dismissal logic and the popup position setting. Trace how dismissal direction is selected for each of the six listed positions and check the behavior across all compositors. Done means each position dismisses toward its corresponding screen edge without breaking drag dismissal.

Written by the indexing model from the issue text.