Setting window.customTitleBarVisibility to windowed in web hides title bar

[grgar]

Does this issue occur when all extensions are disabled?: Yes

• VS Code Version: 1.87.2
• OS Version: macOS 14.4.1

Steps to Reproduce:

1. Open https://vscode.dev

2. Set user settings.json to

   {
       "window.customTitleBarVisibility": "windowed"
   }

3. Title bar is hidden.

Title bar should never be hidden by this option in VS Code Web. This configuration option is considered unknown and should have no effect in web. Other values ("auto", "never") correctly have no effect.

Screen.Recording.2024-03-29.at.9.32.11.PM.mov

This causes problems when using settings sync from desktop because hiding the title bar is fine on desktop where the menu bar is still accessible, but the menu bar is part of the title bar in web and makes it inaccessible.

Version: 1.87.2
Commit: 863d258
User Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/605.1.15 (KHTML, like Gecko) Version/17.4 Safari/605.1.15
Embedder: vscode.dev

[grgar]

It is already impossible to hide the title bar on web in other ways, e.g. Hide Custom Title Bar command, since the configuration option is unregistered.

Raised a PR #209162 to no longer try to read this unregistered configuration option on web.