Replace local absolute skill-creator link with portable reference

[f0d010c]

Hi! I was testing Codex skill repos for publish-readiness and noticed a small portability issue.

project-skill-audit/SKILL.md has a link to a local absolute path:

[$skill-creator](/Users/dimillian/.codex/skills/.system/skill-creator/SKILL.md)

That works on the author machine, but will be broken for anyone else installing or browsing the skill. A relative docs link, plain $skill-creator mention, or a short note would make this portable.

Hope this is useful.

[f0d010c]

Small follow-up for context: the checker I used is now published, and I added a tiny demo repo showing the scaffold -> lint -> smoke -> CI flow:

https://github.com/f0d010c/codex-skillforge-demo

No pressure to use it here; sharing in case it is helpful for future Codex skill maintenance.