Function phase_detect_consumes_cycles 

pub fn phase_detect_consumes_cycles(
    groups: &BTreeMap<String, Vec<usize>>,
    parsed: &[ParsedFile],
    unit_consumes: &HashMap<String, Vec<String>>,
    errors: &mut ErrorSink,
)

Phase 5c: detect consumes cycles. #696: record each consumes-clause site (file + span) keyed by (consumer, target) so a detected cycle anchors on the exact clause that forms the closing edge — a real span in a real file — and renders with source context. Synthetic units are left out so their (snapshot-less) files never claim a diagnostic.