Function agents_md_path 

pub fn agents_md_path(project_dir: &Path) -> PathBuf

Return the path where Codex reads project-level instructions.

AGENTS.md lives in the project root and is the cross-tool standard (Codex, Copilot, Cursor). We do NOT fall back to the deprecated codex.md / .codexrules names — they are pre-consolidation legacy and new installs should target AGENTS.md.