When someone opens a referral link, the app remembers the recruiter's code for a limited time. The person can connect a wallet afterwards. On connect, and after the wallet signs in, the wallet is linked to that recruiter and joins the squad. A new member chooses whether they join as a creator, a trader or both.
A wallet is linked to one recruiter at a time. A wallet that already has a recruiter keeps it, and an opened link for another recruiter does not replace it.