nx_p256_comb.nx

nx_p256_comb.nx -- fixed-base windowed scalar multiplication for the NIST P-256 generator G. Replaces the 256-doubling double-and-add for k*G (the dominant ECDSA-sign cost) with a precomputed table: table[win][d] = d * 2^(4*win) * G for win in 0..63, d in 0..15 k*G = sum over the 64 hex digits of k of table[win][digit_win]. ~64 point additions, ZERO doublings at sign time. The table is built ONCE (deterministic -- multiples of the fixed G) and stored Jacobian (X,Y,Z = 24 i64 = 192 bytes/entry; 1024 entries = 192 KiB) so the build needs no per-entry inversion. Sharing model (NishiLang has no module-level mutable state): a tiny generator tool writes the table to a file once; the signer reads it (sys_read_file) and falls back to the generic double-and-add when the file is absent (e.g. ACME/JOSE callers outside the sites daemon). Verified vs p256_scalar_mul over random scalars in nx_p256_comb_test. license_tier: INDEPENDENT_REDERIVE