Fix a bug where bestValue could decrease during quiescence search pruning, producing non‑monotonic values observed in practice.
Keeping bestValue monotonic prevents inconsistent alpha/beta updates and improves stability of transposition table entries.
The change mirrors the Stockfish patch (dev-20260106-c27c1747) to avoid bestValue going down in the SEE pruning branch.
Description
Update the SEE pruning branch in Search::Worker::qsearch (src/search.cpp) to use bestValue = std::max(bestValue, std::min(alpha, futilityBase)) instead of assigning std::min(alpha, futilityBase) directly.
This ensures the pruning path if (!pos.see_ge(move, alpha - futilityBase)) cannot lower the current bestValue.
The change is a single-line logic fix and does not alter other qsearch behavior.
Testing
No automated tests were executed as part of this rollout.
