RRF merge: add tests, fix warnings, re-run benchmarks
- Add tests for router (zero-group guard), config (YAML parse, policy
display), task registry stub, reshard (time window, throttle, CV),
topology (nodes iterator, auto-derived groups), and task pruner
(gauge lock serialization)
- Fix config validation: minimal YAML now passes CDC cross-field check
- Remove unused import and mut warning in merger/scatter tests
- Re-run score-comparability benchmarks with RRF strategy
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
8eeba0f76b