Add year-over-year trends + expanded ratios (EBITDA, turnover, FCF conversion)

Add deterministic computed-ratios layer (Approach 2); FinanceBench 20% -> 45%

Add hybrid RAG: XBRL structured-financials layer for numeric questions

Fix cold-start crash: probe vector store via filesystem, not a Chroma client

FinChat: RAG chatbot over SEC 10-K filings