Minor fix in creating you first agent docs

[leapingturtlefrog]

Probably the dumbest first Codebuff PR.

Additional Codebuff checks:

[Update Subgoal]
Status: COMPLETE
Log: Completed extensive search across codebase. Found the original issue was already fixed in creating-your-first-agent.mdx. Searched through multiple files and patterns but did not find any other instances of the @ prefix error. The codebase appears to correctly use the format 'publisher/agent@version' without an @ prefix in command examples.

99 credits used for this request.
codebuff-alex > /

[jahooma]

Thanks Alex!!

[jahooma]

We need lots of help with our docs haha