[WIP] Fix failing GitHub Actions job Open or update Release-plz PR

[Copilot]

• Inspect failing GitHub Actions run and job logs for "Open or update Release-plz PR"
• Identify root cause from workflow/action output
• Implement the smallest possible repository fix
• Add or adjust focused tests if applicable
• Run targeted validation (and broader checks as needed)
• Re-run/verify quality checks and summarize results