docs(eval): Fix 2 SearchTool query expansion — attempted and reverted

feat: expose reranker scores through retrieval pipeline

feat: add grounded refusal gate based on retrieval score threshold

fix: wire top_k/strategy through orchestrator to SearchTool, add RAG integration test

fix: handle malformed top_k in SearchTool, add registry dispatch test

feat: Day 2 — tool system with registry, calculator, and search