fix (docs): update createAI example, move AI to separate module

[huozhi]

What & Why

Server action module (the module conatining "use server" on the top level) should only contain server actions but the AI component itself is not. So that's why I want to move it outside of actions.tsx and leave it as a file or a module only containing actions with top-level directive convenience.

Related issue: #2948
Related Next.js issue comment: vercel/next.js#69756 (comment)

[nicoalbanese]

thanks for this @huozhi! I've repro'd and it seems possible to solve by moving the 'use server' directive to the specific function rather than at the top level of the file.

[huozhi]

Hey @nicoalbanese, provding more context here about the PR: I dicussed with @shuding about this, server action module (the module conatining "use server" on the top level) should only contain server actions but the AI component itself is not. So that's why I want to move it outside of actions.tsx and leave it as a file or a module only containing actions with top-level directive convenience.

On Next.js side we'll keep exploring the approaches to warn/error on that, and will address the regression of this case on 14.2. 🙏

[lgrammel]

Approved @nicoalbanese are you looking into the other cases?

[nicoalbanese]

@lgrammel yes