PR #30136 review item O5: docker/entrypoint.sh is now a thin shim
that forwards to stage2-hook.sh — the real ENTRYPOINT is /init plus
main-wrapper.sh. External scripts that hard-coded entrypoint.sh as
the container's ENTRYPOINT will see the cont-init bootstrap happen
but the CMD will not be exec'd (because stage2-hook only handles
bootstrap; main-wrapper.sh handles the CMD passthrough).
Add a stderr warning explaining the new contract and pointing
callers at the migration path (drop the --entrypoint override).
The shim itself stays in place for one release cycle so the
deprecation isn't a hard break — anyone still invoking it sees
the warning in their logs and has time to migrate.
04bdbce906