Add Zenodo concept DOI and date-released to CITATION.cff

[medley56]

Summary

CITATION.cff declared no persistent identifier, so GitHub's "Cite this repository" widget and cffconvert produced citations carrying only the repository URL.

This adds the Zenodo concept DOI (10.5281/zenodo.7735001) via an identifiers: block, and adds date-released so generated citations carry a year.

Closes #280

Why the concept DOI and not a version DOI

A version DOI was deliberately rejected. The ordering of the release process makes it unusable:

1. Release checklist step 3 hand-edits CITATION.cff.
2. Release checklist step 6 pushes the tag.
3. Zenodo mints the version DOI only after it archives the tagged release — i.e. after step 6.

So at the moment CITATION.cff is edited, the version DOI for the release being prepared does not exist yet. A top-level doi: key would therefore routinely ship pointing at the previous release — a persistent identifier that resolves to the wrong software, which is worse than no DOI at all.

The concept DOI is version-agnostic, always resolves to the newest release, and requires no maintenance. It is the same DOI already linked from the README badge.

date-released and keeping it fresh

Without date-released, the BibTeX/APA exports have no year, and the year is not derivable from anything else in the file. A citation with a DOI but no year is still defective.

The value is quoted (date-released: "2026-09-13") on purpose: the CFF 1.2.0 schema types date-released as {"type": "string", "format": "date"}. Unquoted, YAML parses 2026-09-13 into a date object, which fails strict validation.

To stop it going stale, release-checklist step 3 in docs/source/developers.md — which already required a manual edit of CITATION.cff — has been widened to cover the new field. This adds no new step to the release process, only a wider existing one.

Known residual risk, stated plainly: scripts/check_metadata.py does not validate date-released. It reads only title, description, version, license, authors, and maintainers. So a forgotten date-released will go stale silently — nothing in CI will catch it. This was judged acceptable for a date (a minor inaccuracy in a citation year) but would not have been acceptable for a DOI, which is a second reason the version DOI was rejected.

Note for reviewers: pre-existing CFF schema violations (not introduced here)

While verifying this change against the published CFF 1.2.0 schema I found that CITATION.cff does not currently validate, and did not before this PR either. Validating the unmodified file from main produces the identical errors:

• root key description is not a valid CFF 1.2.0 key (the CFF field is abstract, which the file also has)
• root key maintainers is not a valid CFF 1.2.0 key (the CFF analogue is contact)
• orcid values must be full https://orcid.org/… URIs, not bare identifiers
• the required message key is absent

Consequence: cffconvert refuses to convert the file at all, so the DOI added here will not reach a cffconvert BibTeX export until those are fixed. (GitHub's own widget is more lenient.)

I confirmed the additions in this PR are themselves schema-correct by validating a scratch copy with only the pre-existing offenders corrected — that copy validates cleanly and its BibTeX contains both doi = {10.5281/zenodo.7735001} and year = {2026}.

I did not fix those pre-existing issues here, because they are out of scope for #280 and, more importantly, they are coupled to tooling: scripts/check_metadata.py reads the description and maintainers keys directly, so removing or renaming them would break the check-space-packet-parser-metadata hook. That deserves its own PR that changes both files together. Happy to open a follow-up issue.

Verification

• pre-commit run --all-files — all hooks pass (prettier does not process .cff and left the file untouched)
• pre-commit run check-space-packet-parser-metadata --all-files — passes
• date-released confirmed to parse as str, not datetime.date
• Docs build (make html) succeeds
• No version bumps; ships under ## [Unreleased]

🤖 Generated with Claude Code

[medley56]

Two follow-ups on this branch since the PR was opened:

1. The pre-existing CFF validity problem now has a ticket: #285.

To be explicit about what is and isn't in this PR: CITATION.cff does not validate against the CFF
1.2.0 schema, and did not before this change either — the unmodified file from main fails
identically with Additional properties are not allowed ('description', 'maintainers' were unexpected). That is out of scope here because fixing it requires changing scripts/check_metadata.py
in the same commit (it reads both of those keys, and the check-space-packet-parser-metadata hook
runs with always_run: true). #285 has the details.

2. Softened the CHANGELOG entry (bdb783c).

The original entry said the DOI would now appear in cffconvert's BibTeX/APA exports. That is not
true today — cffconvert rejects the document outright for the reasons above, so it emits nothing at
all. The entry now claims only what actually happens: the metadata carries the identifier and the
release year, and GitHub's "Cite this repository" widget reads both. The cffconvert half becomes
true once #285 lands.

The DOI itself is verified correct: validating a corrected scratch copy of the file produces
doi = {10.5281/zenodo.7735001} and year = {2026} in the BibTeX output, so the additions in this PR
are schema-correct — they are just sitting in a document that has other problems.

🤖 Generated with Claude Code

[Copilot]

🟡 Changes recommended

Clarify the changelog claim about cffconvert exports.

Get a fresh assessment by requesting another Copilot review.

Pull request overview

Adds Zenodo citation metadata and documents the release-date update process.

Changes:

• Adds the Zenodo concept DOI and quoted date-released.
• Updates release checklist guidance.
• Documents the change in CHANGELOG.md.

File summaries

File	Summary
docs/source/developers.md	Updates release checklist instructions.
CITATION.cff	Adds DOI and release date metadata.
CHANGELOG.md	Records the citation metadata change; scope the converter-export claim appropriately.

Review details

• Files reviewed: 3/3 changed files
• Comments generated: 1
• Review effort level: Lite

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 94.62%. Comparing base (c55e513) to head (5dbc3c1).

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #284   +/-   ##
=======================================
  Coverage   94.62%   94.62%           
=======================================
  Files          49       49           
  Lines        4203     4203           
=======================================
  Hits         3977     3977           
  Misses        226      226           

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[Copilot]

🟢 Approval recommended

No unresolved blocking issues were identified.

Review details

• Files reviewed: 3/3 changed files
• Comments generated: 0 new
• Review effort level: Lite