How to handle errors?

Thank you for this lib!

What is the proper way to handle errors, if any?
Are you open to PRs in this sense? We can discuss the details together.
Ideally we would like an error listener into the Builder options. Then I would need your help to figure out where to catch these errors in the first place.

The issue names no files or tests. Start by tracing the Builder options and the library's error-producing paths, then clarify which errors should be exposed and how an error listener should be configured. Done requires an agreed scope and defined error-handling behavior before implementation.

索引モデルが issue の本文から書いたものです。