cache: npm caused ~4min ETIMEDOUT on every run (cache service unreachable).
Commit messages containing backticks were shell-expanded inside the
curl -d "..." string, causing 'sha: No such file or directory'. Fixed by
writing release notes to a temp file and using python3 to build the JSON
payload, then passing it to curl with --data @file.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
