nx_u4096_mul_test.nx

nx_u4096_mul_test.nx -- KAT for the 4096x4096 -> 8192 wide-multiply. Mirrors nx_u256_mul_test cases, scaled to 256-limb wide buffer. All five algebraic-identity cases that prove a schoolbook multiplier is correct: - 0 * 0 = 0 - 1 * 1 = 1 - 3 * 5 = 15 (small * small) - 0xFFFFFFFF * 0xFFFFFFFF = 0xFFFFFFFE00000001 (well-known limb-saturation square, exercises carry from limb 0 to limb 1) - 2^32 * 2^32 = 2^64 (single-bit cross-limb) - 2^4096 - 1 squared (exercises full 256-limb wide range; high limb 255 must be non-zero, exercising last carry-out) - shl1 round-trip on wide buffer expect_exit: 0 license_tier: ORIGINAL