Agent Skills: changelog

Maintain a project's CHANGELOG.md in Keep a Changelog 1.1.0 format - record only what moved the project's user-facing surface (commands, flags, API, config, output, screens) and never internal work, pick the right category, word it for the humans who use the project, and insert it under [Unreleased] without disturbing the rest of the file. Also cuts a release section (promotes [Unreleased] to a dated version and updates the compare links) and creates CHANGELOG.md for a project that has none. Use when the user asks to add or write a changelog entry, update the changelog, record a change in CHANGELOG.md, or prepare a release section. Reads git but never commits, tags, or bumps version files.