style: fix ruff lint — import sorting, line length

fix: rerank_score falsy-value bug and double-getattr cleanup

feat: enrich SearchTool metadata with scores, previews, PII count

feat: expose reranker scores through retrieval pipeline

fix: mypy errors — type annotations for pii_redactor, JSONResponse returns

fix(security): add security to /ask/stream, wire PII redactor into SearchTool

feat: add grounded refusal gate based on retrieval score threshold

fix: retrieval metrics use ranked sources, LLM judge wired, report complete

feat: Day 6 — serving layer with FastAPI app, routes, middleware

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