Allow rerunning the theme setup

When you first run Claude Code, you are asked to select a theme and given a visual display of what that theme will look like. However, when later running /config and selecting themes, you just get the words and no visuals, which means that if you want to see if the theme looks good, you have to get Claude Code to work on some code so that it shows a diff. Then if the diff is unreadable, you need to quit and repeat the process again until you find the theme you like.

Please allow us to just rerun the theme setup.

e.g. /theme or something would be fine.