chore(.gitignore): ignore agent files

[Fdawgs]

See fastify/fastify#6474.

Will roll this out to the rest of the repos.

Checklist

• commit message and code follows the Developer's Certification of Origin
  and the Code of conduct

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[Fdawgs]

@mcollina any others you can think of? I saw a .githuman/ one knocking about somewhere?

[ilteoood]

Why are we excluding them?
Wouldn't be better instead to version them in order to provide a sort of "fastify agent", with the right knowledge?
It would also help us with the review process, especially if copilot has the right knowledge

[jean-michelet]

Our policy regarding AI code generation is somewhat ambiguous.
We want to avoid AI slop, but some of us use these tools extensively.

What we want to discourage is people running agents to fix imaginary bugs, long code reviews on changes pushed by authors who do not understand what they submitted and likely just prompt our feedback to an AI agent.

[jean-michelet]

fastify/fastify#6359

[jean-michelet]

Wouldn't be better instead to version them in order to provide a sort of "fastify agent", with the right knowledge?

Open a proposal, we can provide that for end users in docs, fastify-cli or even in the demo.