[Corn Flakes] C++ fix flaky test: ensure generate_random_even_number returns even numbers

[Copilot]

generateRandomEvenNumber() had an embedded 5% flaw that added 1 to the result, producing an odd number. With 20 test iterations, this yielded ~64% failure rate — matching the observed 60% in CI.

Change

• cpp/src/random_math_operations.cpp: Removed the flaw. Function now unconditionally returns dist(gen) * 2.

// Before
int number = dist(gen) * 2;
std::uniform_real_distribution<> flaw(0.0, 1.0);
if (flaw(gen) < 0.05) number += 1;  // ← intentional bug
return number;

// After
return dist(gen) * 2;  // always even, range [0, 100]