nx_mul_wide.nx

nx_mul_wide.nx -- 64x64 -> 128 unsigned MULTIPLIER as a gate-network (fixes the mulh SIL-1 stub; the high-cascade core fundamental that feeds the divider frontier + all crypto + the future LLM -- nx_dimret => INVEST). The sim's MUL cell gives only the LOW 64 bits (it wraps). The full 128-bit product is assembled from 32-bit limbs (each 32x32 partial product < 2^64, so it fits the i64 cell exactly), schoolbook with column carries: a = ah:al, b = bh:bl (32-bit halves; the &MASK32 also undoes arithmetic >>) ll=al*bl lh=al*bh hl=ah*bl hh=ah*bh c0 = ll_lo c1 = ll_hi + lh_lo + hl_lo (carry1 = c1>>32) c2 = carry1 + lh_hi + hl_hi + hh_lo (carry2 = c2>>32) c3 = carry2 + hh_hi lo = c0 | (c1<<32) ; hi = (c2&MASK32) | ((c3&MASK32)<<32) Output: returns the LO net; writes the HI net to hi_out[0]. Reuses nx_alu_divider's div_const/div_op2 cell-builders (DRY). license_tier: ORIGINAL