CDSL Bridge: Hexagonal Nut

Use for a hex body with a centered internal threaded-bore intent.
Invariants: across-flats, thickness, centered bore, and functional lead-in chamfers.
Plan: polygon/hex extrude_add_blind -> centered bore or hole_wizard -> thread audit -> finishing when selectors are valid.
Preserve across-flats separately from thread/bore diameter. Do not create a mating bolt.
Current runtime does not create helical threads; represent the bore and record approximated: thread_geometry_omitted.