Sidecat v0.3.0 Source-only package-authoring milestone. This release marks the first public Sidecat package-authoring source milestone. The main value is the package-authoring pattern: git-workbench is intentionally small, but it is meant to be readable and reusable as a model for wrapping other local CLI tools in Starlark package code. It includes Starlark core packages, Starlark user packages, manifest-bound host capabilities, repo-backed fixtures, local package registry commands, named fixture selection, and the early git-workbench user package with bounded status, diff, stage, unstage, commit, push, plan, and verify behavior. This is not recommended for use. It is not a production runtime, stable command surface, stable package API, hosted service, official binary package, signed binary artifact, SBOM-backed distribution, or provenance-backed binary release. The tag points to 882a95a79915e2d1ee60423e5d59d86d4b7a2a90. Main CI for that commit passed in pipeline 2618317271.