- Clamp KDE candidates to parameter bounds before evaluating l(x)/g(x),
matching the univariate TPE behavior; without this, candidates scored
well at out-of-bounds locations but became suboptimal when clamped
- Sort HashMap iterations by ParamId before consuming the seeded RNG to
eliminate non-deterministic sampling caused by global ParamId counter
- Replace wall-clock timing assertion in async concurrency test with
atomic max-active counter to avoid CI flakiness
- Gate unused HashSet import behind cfg(feature = "async")