nx_pattern_emit6_erf.nx

nx_pattern_emit6_erf.nx -- PATTERN EMITTER: MATH_KERNEL / ERF_TAYLOR (DLMF ch7 rung 1, ME2-ERF-001). The Builder authors f64 erf from the SOVEREIGN spec (nx_mathspec_erf: bf_pi + Newton sqrt, rails held bit-exact vs known-good). The emitter contains STRUCTURE only -- every number written into the module comes from the spec table c[]. kernel: specials (NaN/+-0 sign-preserved/+-Inf->+-1) -> integer-compare domain cuts on |x| bits (positive f64 ordering): |x|>=c[37] (6.0) -> +-1 sub-ulp; |x|>c[36] (1.75) -> NAN_RAW = the RUNG-1 HONEST GAP (erfc route = ME2-ERF-002, named debt; a wrong number is worse than a loud gap) -> else 32-term signed Horner in z=x*x (plain f64, the ch4 core gene) -> EXACT two-product x*p (_er_mul2 27-bit-split dd) -> dd scale by 2/sqrt(pi) (full-bits product + lo-residual tail recombine). Antisymmetry erf(-x) = -erf(x) is BIT-EXACT by construction (odd path only). The emitted test checks ALGORITHM INVARIANTS (specials/cuts/antisymmetry) -- the semantic ULP bar is the Engineer's separate bf-oracle gate (_bf_erf_gate, next). license_tier: ORIGINAL