chore: Adding missing permissions to stale workflow

[devin-ai-integration]

Note

Low Risk
Low risk GitHub Actions change that only adjusts workflow YAML permissions; it should not affect production code but could alter issue/PR automation behavior if misconfigured.

Overview
Adds explicit permissions to the stale.yml GitHub Actions workflow so the reusable stale-closer can write to issues and pull requests.

Also normalizes YAML quoting/formatting for the workflow name and scheduled cron string.

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