[codex] Add CITATION.cff

[gvegayon]

GitHub cannot presently discover structured citation metadata for PyRenew. This pull request adds a root CITATION.cff derived from project metadata and a read-only schema-validation workflow; it does not change package behavior.

Validated with cffconvert --validate and uv build; the source distribution and wheel build successfully, and the source distribution includes CITATION.cff.

Note: This pull request was prepared by GPT-5.6 Terra on behalf of gvegayon.

[github-actions]

Thank you for your contribution @gvegayon 🚀! Your github-pages is ready for download 👉 here 👈!
_{(The artifact expires on 2026-09-18T05:27:08Z. You can re-generate it by re-running the workflow here.)}

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 98.79%. Comparing base (9493a0a) to head (caf1b50).

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #885   +/-   ##
=======================================
  Coverage   98.79%   98.79%           
=======================================
  Files          59       59           
  Lines        2240     2240           
=======================================
  Hits         2213     2213           
  Misses         27       27           

Flag	Coverage Δ
unittests	98.79% <ø> (ø)

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[cdc-mitzimorris]

Thanks!