TextBox with BorderStyle.FixedSingle displays an extra inner border after stopping a debugging session

[Amy-Li03]

.NET version

.NET 11.0.100-preview.7.26365.114 + Private dlls built from Net11/Integration-2 branch of https://github.com/KlausLoeffelmann/winforms repo

Did it work in .NET Framework?

Yes

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

Not support, new feature

Issue description

A TextBox configured with textBox1.BorderStyle = BorderStyle.FixedSingle; may display an unexpected additional inner border after a debugging session is stopped in Visual Studio.
As shown in the screenshot, the control appears to render two borders: the expected outer border and an extra inner border surrounding the text area. This results in a double-border appearance and makes the control look visually incorrect.

Steps to reproduce

1. Create a WinForms application targeting .NET 11 Preview
2. Configure Form's VisualStylesMode = VisualStylesMode.Net11
3. Add a TextBox control to a form with some Text
4. Set textBox1.BorderStyle = BorderStyle.FixedSingle;
5. Start debugging
6. Stop debugging
7. Return to the WinForms Designer and observe the TextBox

[KlausLoeffelmann]

This should be fixed.
Feel free to reopen, if not.