test(cli): Add unit tests for the add command

[K-Sato1995]

Overview

• Extracting the core function of the "add" command into its own function called runAdd.
• Writing basic unit tests for this newly-created function(runAdd).

[vercel[bot]]

@K-Sato1995 is attempting to deploy a commit to the shadcn-pro Team on Vercel.

A member of the Team first needs to authorize it.

[shadcn]

Awesome. I'll probably do same for the other command. Let me label this and get back to it.

[K-Sato1995]

Awesome. I'll probably do same for the other command. Let me label this and get back to it.

@shadcn Thanks! Resolved the merge conflicts! Would love to work on the other commands too.