- Add Z (nuclear charge) and A (mass number) parameters to RadiativeCorrection
- Implement O(Z*alpha^2) finite nuclear size correction per Sirlin 1987:
- Energy-dependent part: ln(m_p) - (5/12)*ln(2W) + 43/18
- Nuclear-structure-dependent part: Delta_F(Z,A) from modified Gaussian model
- Add small-beta Taylor expansion for numerical stability at threshold (beta < 1e-6)
- Extract _safe_beta() and _safe_tanh_inv_beta_over_beta() helper methods
- Remove unused log_wright_bessel import
- Add 14 new tests: Z-dependence, numerical stability, A parameter coverage
- Update docs/06-radiative-corrections.md with new API usage examples
All 70 tests pass. 14 new tests in 3 new test classes.
Local regex-based parser extracts journal, volume, pages for 83% of
references. Supports both local mode (--pdf paper.pdf) and LLM fallback
(--llm) via llama-server API. Includes 319-entry BibTeX in data/.
unzhakov