Function measure_rsqrt

tests/fl/math/fixed_point.cpp:1528–1545

}

AccuracyResult measure_rsqrt() {
    AccuracyResult r = {};
    const int N = 10;  // Spot testing: 10 key points adequate for range coverage (was 50)
    const float lo = 0.01f;
    const float hi = 1000.0f;
    float sumErr = 0;
    for (int i = 0; i < N; ++i) {
        float x = lo + (hi - lo) * i / (N - 1);
        float ref = 1.0f / fl::sqrtf(x);
        float got = s16x16::rsqrt(s16x16(x)).to_float();
        float err = fl::fabsf(got - ref);
        sumErr += err;
        if (err > r.maxErr) { r.maxErr = err; r.worstInput = x; }
    }
    r.avgErr = sumErr / N;
    r.nSamples = N;
    return r;
}

AccuracyResult measure_pow(float exponent, float baseLo, float baseHi) {
    AccuracyResult r = {};