nx_bigint_lib.nx

nx_bigint_lib.nx -- multi-precision integer PRIMITIVES (unsigned), the IMPORTABLE library. Split 2026-07-09 from the nx_bigint.nx / bigint.nx twins (which were code-identical and BOTH carried a main() KAT battery, making them unimportable into any main-bearing binary -- the nx_qa_score_lib precedent). The twins now import THIS lib and keep their main() gates; new consumers (e.g. nx_swcompare_bench) import the lib directly. ZERO imports by design: every primitive is pure limb math on caller-owned buffers (BI3), so this lib is syscall-module-agnostic (safe under both syscalls.nx and nx_syscalls.nx import chains). Representation: array of u32 limbs in LITTLE-ENDIAN order (limb 0 is least-significant 32 bits), stored in i64 slots (low 32 bits used) so 32x32 products and carried sums fit in i64 without overflow. Invariants (from the original): BI1 Limbs past the declared length are never read; callers pass explicit lengths. BI2 Results are written with LENGTH HINTS the caller allocates for (bi_add output needs n+1 limbs). BI3 No heap allocation inside primitives -- caller owns limb buffers. BI4 Comparison returns -1 / 0 / +1 like strcmp. BI5 Arithmetic is UNSIGNED; signed lives at the caller's layer. license_tier: ORIGINAL