Use LLM to Create Stable Release Summaries

We're likely going to have several pre-release versions before a stable release. In the CHANGELOG, all of the changes from the pre-release versions will be tracked. When publishing a stable release, it would be nice to have an LLM go through all the pre-release notes and create a summary of everything for the stable release.

Review the CHANGELOG entries for pre-release versions and the process used when publishing a stable release. Define how the LLM should combine those notes into a stable-release summary and where that summary should appear; done means the stable release includes the generated summary.

Written by the indexing model from the issue text.