fix: address CodeRabbit Phase 5 review feedback

fix: pydantic-ai v1 compatibility and Anthropic model update

fix(phase2): address CodeRabbit review feedback + add examples

fix: resolve mypy divergence between make check and pre-commit

feat(phase2): implement search slice (PubMed, Web, Orchestrator) (#4)

feat(phase1): Foundation & Tooling complete

adds scaffolding