Disabled RichTextBox renders BackColor in padding area but not in client area under NET11 VisualStylesMode

[Olina-Zhang]

.NET version

.NET 11 RC2 build: 11.0.100-rc.2.26455.110

Did it work in .NET Framework?

Not tested/verified

Did it work in any of the earlier releases of .NET Core or .NET 5+?

Occurs after New APIs in .NET11

Issue description

Under VisualStylesMode = NET11, a disabled RichTextBox renders the configured BackColor in the padding area, while the client area continues to use the disabled system background color.
As a result, different background colors are displayed within the same control, creating a visually inconsistent disabled appearance.

No padding value set, only BackColor set:

Set padding to 20, and set BackColor:

Steps to reproduce

1. Create a WinForms application targeting .NET 11.
2. Add a RichTextBox to the form
3. Set Enable to false, set Padding and BackColor
4. Set VisualStylesMode to NET11
5. Run the application to observe