Add Playwright Bing scrape + sentence-level rerank + test_pipeline.py

Add Tavily/Brave/Composite web backends (Wikipedia stays default)

Add 4-tier retrieval pipeline (cache → web → Qwen-verify + date guard → refuse)

Add hallucination-guard (E): pre-gate + V2 cutoff prompt + refusal post-gate

Add runtime/ scripts (SPChat + BGE RAG) for deployment