nx_nofloat_prefix_cache_gate.nx

nx_nofloat_prefix_cache_gate.nx -- proves the PREFIX-KV-CACHE speed optimization is BIT-EXACT + measures the prefill-step savings (operator 2026-07-15: attack the ~2.4 tok/s prefill wall; coordinated with S2 = the compiler owns the per-matmul 4.2x, this owns the ~10x FEWER prefill matmuls for the forge's fixed crib). The forge re-prefills a FIXED crib (~130 tok) on EVERY task. nsv_generate_pfx snapshots the crib's KV rows once and restores them per task, prefilling only the task suffix. This gate proves the load-bearing property: restore-snapshot + suffix-only-prefill produces output BYTE-IDENTICAL to a full prefill (bit-exactness is the whole point of no-float). Same prompt, two paths: A = full prefill, no cache (prefill = nprompt steps) B = full prefill + snapshot rows 0..P (builds the cache) C = restore rows 0..P + prefill [P..nprompt) (prefill = nprompt-P steps) Teeth: T1 output(A) == output(C) BYTE-EXACT (the cache reuse is lossless) T2 cached prefill < baseline T3 savings ratio reported (forge: crib~130 + task~15 => ~10x fewer prefill matmuls) expect_exit: 0 license_tier: ORIGINAL