- Add UserWarning to get_global_news_openai, get_stock_news_openai, and get_fundamentals_openai
- Warnings inform users that OpenAI vendor may hallucinate or provide outdated data
- Recommend alternative vendors: alpha_vantage, google, yfinance, or local
- Add comprehensive test suite to verify warnings are emitted
- Refactor to use shared _warn_hallucination_risk helper function
The issue reported that OpenAI was hallucinating and providing outdated news
(e.g., fake news from November 2025). This is because the OpenAI vendor relies
on the LLM's training data rather than real-time web search. Users should use
alternative vendors for reliable, up-to-date news and fundamental data.
All tests passing (4/4).
006b354829