nx_step_write_gate.nx

nx_step_write_gate.nx -- STEP WRITE round-trip on real twin geometry (cadtwin P3a write half, rung 1). Build the NUT part mesh from as1 via the full v2 pipeline (attribution+tessellation+weld = the organs we built), WRITE it as a faceted-brep STEP with declared mm units + product identity, then READ IT BACK with our own parser + faceted path and require an INTEGER-EXACT round trip (8-decimal fx256 lossless encoding): same triangle count, every corner coordinate identical, known vertex present, units confirmed, product name recovered, deterministic. expect_exit: 0 license_tier: ORIGINAL