Function load_commit_rules 

pub fn load_commit_rules(context_dir: &Path) -> CommitRules

Loads deterministic commit-lint rules from an optional config file.

Resolves .omni-dev/commit-rules.yaml via the standard config priority (local → project → home). Returns CommitRules::default when the file is absent or malformed — never errors, mirroring load_project_scopes.