chore: Adding missing permissions to stale workflow

[devin-ai-integration]

Note

Low Risk
Low risk: workflow-only change that just grants the minimal issues and pull-requests write permissions needed for the stale automation to operate; no product/runtime code is affected.

Overview
Adds an explicit permissions block to .github/workflows/stale.yml granting issues: write and pull-requests: write so the reusable stale workflow can close/update issues and PRs under GitHub Actions’ default restricted token.

Also normalizes the YAML quoting for name and the cron schedule.

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