ToolStripTextBox renders incorrectly when hosted in MenuStrip #14793

.NET version

.NET 11.0.100-preview.7.26365.114 + Private dlls built from Net11/Integration-4 branch of https://github.com/KlausLoeffelmann/winforms repo

Did it work in .NET Framework?

Does not apply - did not exist before.

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

Not support, new feature of #14792

Issue description

When running in Dark Mode with VisualStylesMode = .NET11, a ToolStripTextBox hosted in a MenuStrip is rendered incorrectly.

Unlike the same control hosted in a ToolStrip, the MenuStrip version displays an unexpected light-colored rectangular area on the right side of the text box. The background is not rendered using the Dark Mode color scheme, resulting in an obvious visual artifact.

Steps to reproduce

1. Create a WinForms application.
2. Set VisualStylesMode to NET11.
3. Enable Dark Mode.
4. Add a ToolStripTextBox to a MenuStrip.
5. Run the application.