Function skill_ref_status 

pub fn skill_ref_status(agent_home: &Path, rel_ref: &str) -> SkillRefStatus

Resolve a profile.yaml skill ref to its backing manifest file and report whether it is loadable, missing, or malformed.

Resolution mirrors the runtime loader’s layout rules: modern refs point at a directory (skills/<name>) holding skill.yaml; legacy refs may point directly at a .yaml/.yml/.md file. This is the single source of truth for ref resolution — the Hub loadability badge and the creation-time validation in mur-core both call it.