Address PR #372 R5 review (1 P2)

P2 - docs/references.rst misattributed Baker (2025) "A Practitioner's Guide"
- Wrong author list "Baker, A. C., Larcker, D. F., Wang, C. C. Y., & Wang, X."
  conflates the 2022 JFE staggered-DiD paper (Baker/Larcker/Wang) with the
  2025 arXiv:2503.13323 practitioner's guide. Per the canonical citation in
  diff_diff/guides/llms-practitioner.txt L610-614 and arXiv metadata, the
  actual authors of arXiv:2503.13323 are Baker, Callaway, Cunningham,
  Goodman-Bacon & Sant'Anna.
- Fix: replace the author list (title and arXiv ID unchanged).
- Audit: grep for `Baker.*Larcker|Larcker.*Wang` across docs/, README.md,
  llms.txt, diff_diff/guides/, CHANGELOG.md, CLAUDE.md, CONTRIBUTING.md
  shows no other misattributions.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: igerber

docs/references.rst

@@ -154,7 +154,7 @@ Multi-Period and Staggered Adoption
 
   Primary source for the optimal-weighting / PT-All / PT-Post efficient DiD implemented in our ``EfficientDiD`` class.
 
-- **Baker, A. C., Larcker, D. F., Wang, C. C. Y., & Wang, X. (2025).** "Difference-in-Differences Designs: A Practitioner's Guide." *arXiv preprint* arXiv:2503.13323. https://arxiv.org/abs/2503.13323
+- **Baker, A., Callaway, B., Cunningham, S., Goodman-Bacon, A., & Sant'Anna, P. H. C. (2025).** "Difference-in-Differences Designs: A Practitioner's Guide." *arXiv preprint* arXiv:2503.13323. https://arxiv.org/abs/2503.13323
 
   Source for the 8-step practitioner workflow surfaced via ``diff_diff.get_llm_guide("practitioner")`` and the README ``## Practitioner Workflow`` section. See ``docs/methodology/REGISTRY.md`` for the diff-diff renumbering and per-step deviations.