Can't click button with draggable image as content

### Describe the bug

When setting a button with an image as content, the button will only be clickable where the image doesn't go, like the edges of the button.

### Why is this important?

It's a common scenario to have a clickable image.

### Steps to reproduce the bug

[Link to the repro](https://github.com/eduardobragaxz/DragButtonRepro)

### Actual behavior

Doesn't click if you click the image.

### Expected behavior

Can't click.

### Screenshots

_No response_

### NuGet package version

WinUI 3 - Windows App SDK 1.8.2: 1.8.251003001

### Windows version

Windows 11 (24H2): Build 26100

### Additional context

_No response_

Start by running the linked DragButtonRepro project with Windows App SDK 1.8.2 on Windows 11 and verify the hit-testing behavior. Then trace the WinUI button and image input handling to identify why clicks over the image are not delivered. Done means the button responds when clicking both the image and the surrounding button area.

Written by the indexing model from the issue text.