feat: Follow symlinked skills

[philipp-spiess]

Closes #8369

Skills are an open standard and as such it should be easily possible to share skills across different agents. In my case, that involves setting up skills via symlinks.

This PR tracks symlinks in the skills traversal instead of skipping it. Note that symlinks can be recursive so we have to keep track of visited directories during the skills scan.

Disclaimer that the code is 100% written by GPT-5.2-Codex though :) But I did test it locally:

Before

After

I also ran one of the skills to ensure they work alright!

[github-actions]

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[philipp-spiess]

I have read the CLA Document and I hereby sign the CLA

[etraut-openai]

Thanks for the contribution. We've updated our contribution guidelines to clarify that we're currently accepting contributions for bugs and security fixes, but we're not generally accepting new features at this time. We need to make sure that all new features compose well with both existing and upcoming features and fit into our roadmap. If you would like to propose a new feature, please file or upvote an enhancement request in the issue tracker. We will generally prioritize new features based on community feedback.

[philipp-spiess]

@etraut-openai Hey! Do you have any insights into why this change could be causing issues? Seems like this hardly justifies being called a feature. Codex already supports symlinks for ~/.codex/AGENTS.md so this just seems like an oversight?

[lherron]

Seriously why is this closed and not merged? Why wouldn't we be allowed to symlink to skills?