Apple Container is no longer supported — the runtime abstraction in
src/container-runtime.ts is already Docker-only. Remove the remaining
setup-time branches that probed for it: the Apple Container runtime
option in the container build step, the APPLE_CONTAINER field emitted
by the environment check, and the `command -v container` probe in
verify. `--runtime docker` still parses for backwards compatibility
with the /setup skill.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>