Library generation failed (d706482)

See [failed job](https://github.com/googleapis/google-cloudevents-java/actions/runs/18424900685)

Start with the linked failed job in GitHub Actions and inspect its logs, especially the library-generation step. Identify the generation failure and the relevant build configuration or generator entry point from the job output. The issue is done when the library generation job completes successfully.

索引モデルが issue の本文から書いたものです。