nx_gamesave_gate.nx

nx_gamesave_gate.nx -- CERTIFICATION of the nx_gamesave part (gamebench gap-queue rank 1). A save/load part is only worth composing if the ugly cases are PROVEN, so the teeth are the failure modes that actually ruin players' runs: T1 round-trip fidelity -- every field returns exactly, metadata intact T2 BIT-EXACT re-save -- save->load->save is byte-identical (the determinism exceed, persisted) T3 corruption REFUSED -- one flipped payload byte -> CHECKSUM-CORRUPT, never partial state T4 truncation REFUSED -- a chopped file -> SHORT-TRUNCATED, not a misparse T5 future-version REFUSED -- a newer format is rejected, not silently misread T6 additive-only (rule 13) -- saving over a slot banks the PRIOR BYTES as .prev, verified by content T7 atomic -- no .tmp residue survives a save T8 ANTI-VACUITY -- after all those refusals, a clean save/load must STILL SUCCEED. Without T8 a loader that simply refused everything would score 7/7. This is the tooth that makes the refusal teeth mean something. license_tier: ORIGINAL expect_exit: 0