Navigating to a symbol that's defined in typeshed currently doesn't work when using the vendored typeshed because Red Knot can't create an URL that the client can display (because they're not actual files on disk).

Possible options:

• Extract the typeshed stubs (or just that one file). This should work with all LSP clients
• Use a custom URL (e.g. vendored://) with a custom handler to show such a file (see https://github.com/astral-sh/ruff/pull/16901/files)