_f64_erf_gate_authored.nx

_f64_erf_gate_authored.nx -- f64 EDGE gate for the Builder-authored erf (component 5). Complements the bf oracle gate (semantics) with IEEE edge discipline: E1 denormal in -> finite, sign-preserved, non-NaN (series path: x*p well-defined) E2 monotone non-decreasing over 0.5..1.75 step 1/256 (no Horner wiggle at the top) E3 gap contract: first bits ABOVE the 1.75 cut -> NAN_RAW (loud, never wrong-number) E4 result strictly < 1.0 inside the series domain (erf(1.75)=0.98667...) E5 SEMANTIC ANCHORS (the tamper judge's teeth -- RUNGRUN re-runs THIS gate after flipping a kernel literal, so edge checks alone are blind to coefficient/scale flips that preserve monotonicity): 8-point bf-oracle ULP<=4 at x=k/8, k=1..8, with 2/sqrt(pi) re-derived INDEPENDENTLY (judge diversity, not shared spec). Durable: F64ERF row -> knowledge/status/math_engine.log. Exit 0 iff all held. license_tier: ORIGINAL