Add PortfolioAnalyzer class that runs the full agent pipeline on multiple
stocks and produces a comparative KEEP/REDUCE/EXIT recommendation using
the deep thinking LLM. Includes per-ticker error handling, graceful
degradation on LLM failure, and result logging.
Addresses #60 and partially #406.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
Robin Lindbladh