Add consecutive requeue circuit breaker

[bitwise-aiden]

Summary

• add an independent, disabled-by-default max_consecutive_requeues worker circuit breaker
• count only accepted requeues while preserving the existing consecutive-final-failure semantics
• expose the setting programmatically and through both the Minitest and deprecated RSpec CLIs
• add Redis-backed two-worker integration coverage proving an unhealthy worker is fenced while a healthy worker drains its requeued tests
• document the two circuit breakers and their reset behavior

Testing

• bundle exec rake test (297 tests, 995 assertions, 0 failures)

Closes #406