Issue 142: the mesh compiles its own host and publishes it to its registry

Both of the things ADR 0141's insight named as remaining are built. A Go
toolchain based on a new mesh-tools-go module, so the compiler is named
and not pinned; and ${version} in any value of a resource that uses an
archive or a bundle.

Measured rather than asserted: the mesh built the host through its own
toolchain, published it to its own registry, and the bundle fetched back
out is a statically linked stripped binary that runs and says it is the
host.

The cost was larger again than 0141's note said. Three more things in the
path assumed one language or one shape — an entrypoint became a .ts file
whatever the language, the output directory was the compiler's to create,
and a bundle was refused if it named what it is built from — and a fourth
was in the base image, which is Alpine where the first Dockerfile ran
apt-get. That last one is issue 136 in an image, and the build refused
rather than a module failing later.

The version in a path is the digest, not the commit: two builds of one
commit are the same bytes, so a content-addressed version keeps the path
an unchanged build already had.

Still nothing delivers a version to a machine. The host module declares no
resources, so the bundle sits in the registry and no machine is asked to
take it. 0141 carries the insight and 142 the account.

02-DECISIONS/0141-the-host-delivers-its-own-successor.md

@@ -109,6 +109,23 @@ understated as none. The remaining work is a way to build the host and a way to
 path, and until both exist nothing delivers a version and every machine takes the fallback — which is
 what every machine does today.
 
+> **Progressive insight — 2026-09-30. Both of those exist now.** The paragraph above named two missing
+> things and they are built: a Go toolchain, based on a new `mesh-tools-go` module so the compiler is
+> named and not pinned, and `${version}` in any value of a resource that uses an archive or a bundle.
+> The mesh compiles its own host and publishes it to its own registry, measured — a statically linked
+> stripped binary, fetched back out and run. **The cost was larger again than this note said**: three
+> more things in the path assumed one language or one shape, and a fourth was in the base image.
+> The account is [issue 142](../04-ISSUES/142-the-host-is-the-one-thing-the-mesh-does-not-deliver/01-progress.md).
+>
+> The version in a path is the artifact's **digest**, not the commit this note's own wording would
+> suggest. Two builds of one commit are meant to be the same bytes, so a content-addressed version
+> means an unchanged build keeps the path it had; a commit-named one would move for an identical binary
+> and recreate everything reading it.
+>
+> **Still nothing delivers a version to a machine.** The host is a module and builds, and declares no
+> resources, so the bundle sits in the registry and no machine is asked to take it. That is the next
+> piece, and the decision above is unchanged by any of this.
+
 ## Consequences
 
 - **The host becomes a build target and a module** — a module whose resource is the next host, applied