CI: check for pending releases

[fingolfin]

This adds a weekly workflow using check-pending-release. It opens a single issue (label pending release) when there are commits since the last release that have been left untouched for at least 7 days, so finished work does not go unreleased. Changes to .github and .gitignore do not count. The issue is closed once a release is made; the job added to release.yml makes that happen right after a release made with the release workflow.

See the action's README for details and options, such as the quiet period or ignored paths.

🤖 Generated with Claude Code

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 3.57%. Comparing base (4d50c0b) to head (52c9b91).

Additional details and impacted files

@@          Coverage Diff           @@
##           master      #9   +/-   ##
======================================
  Coverage    3.57%   3.57%           
======================================
  Files          24      24           
  Lines        3244    3244           
  Branches      698     698           
======================================
  Hits          116     116           
  Misses       3128    3128           

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