Web projects offer desktop-only add items (Container Control, Window, Menu Bar, Toolbar)

In a Web project, the Navigator's right-click menu on App (and the Insert menu) offers Add Container Control. The item is created and Studio shows it in the Navigator, but compiling or running the web project fails with the compiler error Unknown superclass 'ContainerControl'.

ContainerControl is a desktop standard-library class and is not available to Web projects, so the add menus should not offer it (or other desktop-only items) there.

Expected behaviour: in a Web project, the add/insert menus offer only source items the Web target can build (Class, Enumeration, Interface, Module, Web Page). Desktop-only items such as Container Control, Window, Menu Bar, and Toolbar are not offered. Desktop projects keep the current behaviour.