PairFiller.EvaluateCandidates wrapped its candidate loop in
FillStrategyRegistry.SetEnabled(...) and reset it with SetEnabled(null)
afterwards. Nothing inside that window re-enters the strategy pipeline
(EvaluateCandidate and FillRemnantBox only use FillLinear), so the
restriction had no effect on the running solve. It did mutate process-global
state: concurrent solves (e.g. benchmark --parallel) could observe the
narrowed strategy list, and the reset cleared any filter set elsewhere.
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>