container-layer

# Container Layer Build a reproducible, cached environment overlay for ephemeral containers using a Dockerfile-like spec. ## When NOT to use this skill This authors and caches a layer spec. It is not a Docker troubleshooting tool. | Situation | Use | |---|---| | A build is slow or failing | read the build log; this skill will not help | | Managing a running container | docker/podman directly | | Session boot sequence and hooks | the workspace's own boot docs | The tell is tense: this skill is for the environment you want next session, not the container you are fighting now. ## Concept The container resets every session, but your environment shouldn't. This skill: 1. Parses a `Containerfile` (Dockerfile subset) that declares your environment 2. Caches the built result as a tarball in GitHub Releases 3. Restores from cache on subsequent boots (single fetch vs. N installs) 4. Provides a `uv` shim that captures ad-hoc installs back into the Containerfile ## Supported Containerfile Instructions ```dockerfile # Environment variables ENV KEY=value # Shell commands (including package installs) RUN apt-get install -y foo # system packages RUN uv pip install pandas numpy # Python packages (preferred) RUN pip install requests # also works # Fetch files from URLs or GitHub FETCH https://example.com/file.tar.gz /dest/path FETCH github:user/repo /dest/path # latest tarball FETCH github:user/repo@ref /dest/path # specific ref # Set working...