v12.0.0

'Breaking: devkit-container is now its own package on SFTPyPI (AetherBreaker/devkit-container). setup-project adds it as a runtime dependency of every project with [tool.docker].services, locks it under the running devkit, syncs the venv and renders docker/Dockerfile from the installed package; docker-pin refreshes a drifted Dockerfile before pinning. The container crate, its Dockerfile template and the container-vN release stream are gone. Rollout per project: poe lock, poe setup-project (answer replace for the Dockerfile), poe docker-pin, push.'