This pull request refactors the GitHub Actions workflow for notifying
about stale Dashboard PRs by replacing custom JavaScript scripts and the
`actions/github-script` action with new TypeScript scripts that
communicate via standard input/output. This simplifies the workflow,
improves maintainability, and adds better error handling, especially for
API rate limits. The Slack notification script is also rewritten in
TypeScript and now reads PR data from stdin, making the workflow steps
more composable.