ctz

    pub fn ctz(a: Const, bits: Limb) Limb {
        // Limbs are stored in little-endian order. Converting a negative number to twos-complement
        // flips all bits above the lowest set bit, which does not affect the trailing zero count.
        if (a.eqlZero()) return bits;
        var result: Limb = 0;
        for (a.limbs) |limb| {
            const limb_tz = @ctz(limb);
            result += limb_tz;
            if (limb_tz != @bitSizeOf(Limb)) break;
        }
        return @min(result, bits);
    }