Function external_ref_node 

pub fn external_ref_node(qualified: &str) -> Node

Build an external-ref placeholder node for a project-qualified target key (<project>::<key>, ADR-0009). The node lives in the referring repo’s store so an inferred edge to the (foreign) target satisfies store integrity; its qualified target is recorded in meta so crate::Workspace::follow_external_ref can resolve it across the workspace. Tagged Provenance::Inferred.