[kaiks]

Summary

• split one Crystalball prediction across parallel RSpec workers
• keep all predicted locations for one spec file on the same worker
• detect Knapsack and parallel_tests worker variables
• allow explicit Crystalball worker configuration for other runners
• prevent the evaluation feature setup from rebuilding its map

Problem

Each parallel worker received the complete prediction. In the end-to-end reproduction, a serial run selected 9 examples, but two workers ran 18 examples in total. This caused duplicate work and could cause test resource conflicts.

Verification

• bundle exec rspec spec features (308 examples, 0 failures)
• Ruby 3.2 focused unit and end-to-end tests (19 examples, 0 failures)
• bundle exec rubocop (192 files, no offenses)
• bundle exec yard --fail-on-warning
• bundle exec rake build

Scope

This PR fixes prediction evaluation. Parallel map generation has a different problem: workers compact and write map fragments independently. That work should use a separate change.