Function client_spans 

fn client_spans(
    service: &EntityDeclaration,
    scan: &DataFrame,
    window: &GraphQueryWindow,
) -> Result<DataFrame>

(timestamp, trace_id, span_id, src_id, status_code, duration_nano, virtual_dst, virtual_conn). src_id is built from the table’s service declaration, so edges land on exactly the entity ids the registry emits (a composite identity renders the same sorted k=v form); the per-table projection is what lets tables with different declarations union.