Add scheduled workflow to clean up stale PR status checks

[Copilot]

Adds automation to keep PR status checks fresh by deleting stale checks and prompting PR authors to trigger new ones. This ensures status checks run on the current codebase state rather than outdated merge commits.

Implementation

• Schedule: Cron 0 0 */3 * * (every 3 days at midnight UTC)
• Trigger: Also supports manual workflow_dispatch
• Files:
  • Workflow: .github/workflows/CleanUpStalePRChecks.yaml
  • Composite Action: .github/actions/CleanUpStalePRChecks/

Logic

1. Query open PRs via gh pr list and filter to MERGEABLE state only
2. For each mergeable PR:
   • Get checks via gh pr checks (using state field)
   • Find the "Pull Request Status Check"
   • If successful (state: SUCCESS) and completedAt > 72h:
     • Delete the stale workflow run via gh run delete
     • Add a comment to the PR with instructions to trigger a new check
3. Display summary as workflow run summary and in logs

Why Delete Instead of Rerun?

Rerunning a workflow run would still use the old merge commit, not reflecting the current codebase state. Deleting the run puts the PR in a "waiting for status checks" state, and the next commit or close/reopen will trigger a fresh check on the current merge commit.

Key Details

• Cross-platform compatible: Uses forward slashes in module import path
• Date parsing uses InvariantCulture for locale safety
• Retry logic: Uses Invoke-CommandWithRetry from EnlistmentHelperFunctions.psm1 with exponential backoff
• Run ID validation using Int64 to handle IDs larger than 2 billion
• Error handling: exits with error code 1 if any PRs fail to be processed
• GitHub Actions notice when no open PRs found
• Workflow run summary using GITHUB_STEP_SUMMARY for better visibility
• Summary includes both successful deletions and failed PRs
• WhatIf mode available in script for testing with accurate messaging
• Automated PR comments provide clear instructions

Permissions Required

permissions:
  actions: write        # To delete workflow runs
  checks: read          # To read PR check status
  contents: read        # To access repository files
  pull-requests: write  # To add comments to PRs

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Pull request overview

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