Add after-check hooks for args and ret; allow runtime check bypass

[gnl]

• Adds the ability to set a callback in the config to receive function input and output when the spec checks are successful
• Allows runtime bypass of checks

It's primarily meant to enable the integration of Guardrails with a particular in-development automatic gen-testing project based on the corresponding Ghostwheel functionality, though it can, of course, also have other uses in the future.

Given that this is probably a rather niche use case, and that further changes to the functionality might be needed as the requirements evolve, I have not added any documentation for now – this can be done later in a separate PR if desired.

[awkay]

I would like to see more of where this is going first. You can use deps local for leveraging your own fork of guardrails for now, and if you get to something useful that needs these then we can add them in. I don't want to add more spurious stuff (like I did for copilot) that is just hanging around waiting to get used, and potentially confusing users.

[gnl]

That makes sense. It's enough for me to know that you'd be okay with merging this when needed, until then I'm perfectly fine working with my own fork.

[gnl]

Closing this as part of it is no longer relevant after the recent Guardrails improvements, and the other part is TBD, will re-submit in the future.