Auto-completion when application works in 2 modes (GUI, CLI) about typer

[mzebrak]

One way I found is to perform additional checks like:

    if not sys.argv[1:] and sys.stdin and sys.stdin.isatty():
        run_gui()

and it works since the sys.stdin.isatty() is False when running from [TAB][TAB],
but I haven't fully tested it yet, and there might be a better way to do this.

EDIT:
Actually, since it looks like _MYAPP_COMPLETE env var is set in every compdef (bash zsh etc.) It is a better way to check if we are in the application from [TAB][TAB]

if not sys.argv[1:] and "_MYAPP_COMPLETE" not in os.environ:
    run_gui()