Add GitHub Action to validate issue/PR template compliance

[rodrigobnogueira]

What do these changes do?

Adds a Check Template GitHub Actions workflow (.github/workflows/check-template.yml) that automatically validates issue and PR descriptions against the repository templates.

For issues (bug reports):

• Detects version fields left at the default placeholder (e.g. $ python --version with no actual output)
• Detects empty required sections (Describe the bug, To Reproduce, Expected behavior)
• Handles the legacy markdown issue template (ISSUE_TEMPLATE.md)

For PRs:

• Checks that the template sections are present ("What do these changes do?", "Checklist")
• Detects a blank "What do these changes do?" section
• Rejects PRs opened from the fork's default branch (inspired by bdraco's suggestion)

When violations are found, the workflow:

1. Applies the invalid label for triage
2. Posts an explanatory comment listing all problems
3. Closes the issue/PR

Safeguards:

• Skips bot-authored submissions (dependabot, pre-commit-ci, etc.)
• Avoids duplicate comments on re-edits (updates the existing comment instead)
• Maintainers can bypass validation by applying bot:chronographer:skip or backport:skip labels

Prior validation on fork:

• Invalid issue — closed by bot
• Valid issue — left open
• Invalid PR — closed by bot
• Valid PR — left open

Are there changes in behavior for the user?

No changes to the library itself. This only affects the GitHub repository workflow for contributors: issues and PRs that do not follow the templates will now be automatically flagged and closed with a comment explaining what needs to be fixed.

Is it a substantial burden for the maintainers to support this?

No — this is a standalone GitHub Actions workflow with no dependencies on the codebase. It can be disabled by simply deleting the file or adding a workflow_dispatch condition. The label-based bypass mechanism means maintainers can override it at any time.

Related issue number

Fixes #12163

Checklist

• I think the code is well written
• Unit tests for the changes exist
• Documentation reflects the changes
• If you provide code modification, please add yourself to CONTRIBUTORS.txt
• Add a new news fragment into the CHANGES/ folder

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 98.94%. Comparing base (7eb0e80) to head (b836e74).
⚠️ Report is 2 commits behind head on master.
✅ All tests successful. No failed tests found.

Additional details and impacted files

@@           Coverage Diff           @@
##           master   #12541   +/-   ##
=======================================
  Coverage   98.94%   98.94%           
=======================================
  Files         131      131           
  Lines       46622    46622           
  Branches     2414     2414           
=======================================
  Hits        46132    46132           
  Misses        367      367           
  Partials      123      123           

Flag	Coverage Δ
Autobahn	22.44% <ø> (ø)
CI-GHA	98.91% <ø> (ø)
OS-Linux	98.67% <ø> (+<0.01%)	⬆️
OS-Windows	97.03% <ø> (ø)
OS-macOS	97.93% <ø> (-0.01%)	⬇️
Py-3.10.11	97.42% <ø> (-0.01%)	⬇️
Py-3.10.20	97.91% <ø> (ø)
Py-3.11.15	98.15% <ø> (-0.01%)	⬇️
Py-3.11.9	97.68% <ø> (+<0.01%)	⬆️
Py-3.12.10	97.76% <ø> (ø)
Py-3.12.13	98.25% <ø> (ø)
Py-3.13.13	98.47% <ø> (+<0.01%)	⬆️
Py-3.14.4	97.78% <ø> (-0.66%)	⬇️
Py-3.14.5	98.05% <ø> (?)
Py-3.14.5t	97.54% <ø> (+<0.01%)	⬆️
Py-pypy3.11.15-7.3.21	97.41% <ø> (-0.02%)	⬇️
VM-macos	97.93% <ø> (-0.01%)	⬇️
VM-ubuntu	98.67% <ø> (+<0.01%)	⬆️
VM-windows	97.03% <ø> (ø)
cython-coverage	37.94% <ø> (ø)

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[codspeed-hq]

Merging this PR will not alter performance

✅ 72 untouched benchmarks
⏩ 69 skipped benchmarks¹

---

_{Comparing rodrigobnogueira:check-template-12163-v2 (b836e74) with master (7eb0e80)²}

Footnotes

1. 69 benchmarks were skipped, so the baseline results were used instead. If they were deleted from the codebase, click here and archive them to remove them from the performance reports. ↩

2. No successful run was found on master (125dfae) during the generation of this report, so 7eb0e80 was used instead as the comparison base. There might be some changes unrelated to this pull request in this report. ↩

[Dreamsorcerer]

I'm even more concerned about this now, as we have AGENTS.md ensuring that AI contributions follow the template now, and this week I've seen a couple of obviously human-written PRs that didn't follow the template, and I'm grateful they didn't make me read through the whole template for what could be said in 1 line.

This will now only close human PRs. I've also now unsubscribed from PR notifications, so I have no way to audit this workflow and know that legitimate PRs are getting closed incorrectly.