[Placeholder] Adoption of Apache Iceberg Verification

Consider adopting [Apache Iceberg Verification](https://github.com/apache/iceberg-verification) once its initial fixtures are ready for integration. The project aims to provide shared, language-neutral conformance fixtures with expected values derived from the Iceberg specification, helping detect inconsistencies across implementations.

The original discussion ML thread: https://lists.apache.org/thread/8wsvnhktw27h0tqnxljzmnsogwd52tjj

Start with the Apache Iceberg Verification repository and the linked mailing-list discussion; the issue names no local files or tests. Confirm when its initial fixtures are ready, then identify the iceberg-cpp integration entry point. Done means the shared verification fixtures have been adopted by iceberg-cpp.

Written by the indexing model from the issue text.