Function validated_pending_in 

pub fn validated_pending_in(
    root: &Path,
) -> Result<Vec<(String, Pending)>, Vec<String>>

Read and validate the pending files under root/design/pending (skipping README.md), sorted by filename. Root-parameterised so the stamp — and its fixture tests — can target any tree; check_all is this over the real repo_root.

Also cross-checks each file’s closes_rule entries against known_rule_ids — a syntactically valid id (is_rule_id, checked in validate) that names no rule the reference actually has is still an error, just one that needs root to catch, which the pure per-file parse doesn’t have.