The installer carries a builder and builds the control plane it raises

It carried the thing it was going to run; it now carries the thing that makes
it. One artifact either way — but a mesh raised this way holds a control plane
it built from a repository and a commit it can name, and can therefore build
again. A mesh handed a finished image could not, and had no way to find that
out until somebody needed it to.

A build step sits between load and bundle, because the bundle must name an
image and that image no longer arrives finished. Everything after it is
unchanged: a locally built image is named by the digest of its own
configuration, which is exactly what the carried one was named by.

Refused in preflight when nothing says what to build, so a run that cannot
finish says so before it has changed anything.

.gitignore

@@ -3,4 +3,4 @@
 /dist/
 # The placeholder `make bootstrap` moves aside while a saved image is embedded. Ignored so an
 # interrupted release build cannot commit a twenty-megabyte tar by accident.
-/internal/image/control-plane.tar.placeholder
+/internal/image/builder.tar.placeholder