chore: add workflow to close stale PRs with failed workflows

[DenizAltunkapan]

• I have read CONTRIBUTING.md.
• This pull request is all my own work -- I have not plagiarized it.
• All filenames are in PascalCase.
• All functions and variable names follow Java naming conventions.
• All new algorithms have a URL in their comments that points to Wikipedia or other similar explanations.
• All new code is formatted with clang-format -i --style=file path/to/your/file.java

@alxkm Adds a GitHub Actions workflow to automatically close PRs with failed workflows that have been inactive for 2 weeks.

• Ignores merges from main/master; only PRs without relevant commits are affected.
• Adds a comment explaining why the PR was closed and how to reopen it.
• Complements the existing stale workflow (30 days), cleaning up broken PRs earlier.

Helps keep the repository clean and reduces CI load.

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 78.20%. Comparing base (2da0465) to head (1ad4f19).

Additional details and impacted files

@@            Coverage Diff            @@
##             master    #6927   +/-   ##
=========================================
  Coverage     78.20%   78.20%           
  Complexity     6563     6563           
=========================================
  Files           743      743           
  Lines         21886    21886           
  Branches       4284     4284           
=========================================
+ Hits          17115    17117    +2     
+ Misses         4087     4086    -1     
+ Partials        684      683    -1     

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[alxkm]

@DenizAltunkapan thank you for this good contribution, which will help keep this repository updated.
This would be nice as a configurable GitHub policy, but your workflow should solution works well also.

However, it can't be merged right now because our branch protection rules require merging through the GitHub UI, and there are some repository rule blocking the merge. We'll need to address these requirements before we can proceed with merging PR.