PR-Issue link check

[glageju]

Summary

Adds a reusable GitHub Actions workflow that validates PR descriptions contain a valid linked issue reference. This enforces the practice of tying every pull request to an issue for better traceability.

Type of Change

• New feature (non-breaking change which adds functionality)
• CI/CD changes

Changes

• Added workflows/check-pr-issue-link.yml — a new reusable workflow that:
  • Triggers on pull_request events (opened, edited, reopened, synchronize) and supports workflow_call for cross-repo use within the StacklokLabs organization
  • Parses the PR body for closing keywords (closes, fixes, resolves and variants) referencing issue numbers
  • Validates referenced numbers are real issues (not PRs or non-existent)
  • Posts/updates/removes a sentinel-tagged warning comment depending on the result
  • Manages a needs-issue-link label to flag PRs missing a valid link
  • Uses concurrency groups to cancel in-progress checks on the same PR

Testing

• Manual testing

Closes #1
Fixes #2

[github-actions]

Invalid Issue Reference

• #2 does not exist in this repository
• #1 is a pull request, not an issue

Please update the PR description to reference a valid issue.

[lorr1]

Can you add a sentence as to why it requires write permissions if you know.