CITATION.cff carries no release version or date — wire it into the release tooling, or add a DOI for citable releases #967

CITATION.cff (added in #964) deliberately omits version and date-released, because nothing would keep them in sync: the released version is single-sourced in pyproject.toml, and the only other mirror of a released version — the marketing site — is guarded by tools/update_site_version.py --check. Adding a literal here without extending that tool would create exactly the un-guarded duplicate docs/standards/release.md exists to prevent.

The cost of omitting it: GitHub's "Cite this repository" panel emits a citation with no year, an undated APA string and a placeholder BibTeX key. For a project whose selling point is reproducibility, that is weak.

Two ways to close this, and they compose:

1. Extend the release tooling. Teach tools/update_site_version.py (or a sibling) to rewrite version: in CITATION.cff from the same CHANGELOG.md header it already reads, and add it to the --check step in docs/standards/release.md and the cut-release skill — keeping the .claude/ and .agents/ skill mirrors in parity (the skill-parity guard checks this).
2. Add a DOI for citable releases (Zenodo's GitHub integration, or a manual deposit). A DOI is version-independent, so nothing has to be kept in sync at all.

Acceptance criteria:

• CITATION.cff either carries version/date-released that the release tooling rewrites and --check verifies, or records a DOI and links the Zenodo record.
• docs/standards/release.md names the new step, or states explicitly that the DOI makes the step unnecessary.
• If the tooling route is taken: a test covering the rewrite, and .claude/skills/ and .agents/skills/ stay in parity.