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 90.12%. Comparing base (88ce719) to head (f0fb918).

Additional details and impacted files

@@           Coverage Diff           @@
##           master      #41   +/-   ##
=======================================
  Coverage   90.12%   90.12%           
=======================================
  Files          22       22           
  Lines        2370     2370           
=======================================
  Hits         2136     2136           
  Misses        234      234           

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.