Enable changelog for all TypeSpec emitters

Currently, our TypeSpec emitters do not include a changelog file to track changes across emitter upgrades.
This makes it difficult to accurately track version information. Given that these emitters are official tools we publish to customers, it would be beneficial to introduce a changelog file.
In addition, EngSys should provide a template to ensure the changelog is consistently updated with each release.

Start by inventorying the official TypeSpec emitters and locating any existing changelog conventions in the repository. Define the shared EngSys template and add a changelog for each emitter, with completion confirmed when every official emitter has one and the template supports consistent release updates.

Written by the indexing model from the issue text.