Is res_multistep_kl_optimal sampler in forge?

Is the res_multistep_kl_optimal sampler in forge? And if not how would I be able to add it to Forge?

The issue names the res_multistep_kl_optimal sampler but no files, tests, or entry points. First locate existing sampler definitions and the Forge integration path, then determine whether this sampler is already available. Done would require a clear implementation or integration plan, with tests or documentation showing how it is exposed.

Written by the indexing model from the issue text.