Library generation failed (3b86441)

See [failed job](https://github.com/googleapis/google-cloudevents-java/actions/runs/17510415358)

Start with the linked failed job for commit 3b86441 and inspect its logs to identify which library-generation step failed. Trace that step to the relevant project entry point, reproduce the failure if possible, and consider the issue done when library generation completes successfully in the job.

索引モデルが issue の本文から書いたものです。