Completion scripts for zsh (--generate-completion-script) include completion for hidden subcommands, making them not very hidden.

I don't think this is a regression. In my testing, hidden arguments were correctly hidden in completion.

Checklist

• If possible, I've reproduced the issue using the main branch of this package
• I've searched for existing GitHub issues

Steps to Reproduce

• create a command with subcommands
• make one of the subcommands be hidden
• generate and load completion for the command in your shell of choice (I used zsh)
• navigate through the completion options for the base command

Expected behavior

Hidden subcommands should not be displayed.

Actual behavior

Hidden subcommands get displayed.