Rename mesh-control -> mesh-controller, substrate -> foundation

One name per thing, per the HQ glossary: the module/container/image/binary/repo
becomes mesh-controller, the seat the-controller, and the store+broker pair the
foundation (embedded base bundles, default template and example lock renamed with
their go:embed directives). No behaviour change — a pure vocabulary rename.

Claude-Session: https://claude.ai/code/session_01D6qtiYU3P9jk3pnAXyAFyx

scenarios/plex-node.yml

@@ -1,7 +1,7 @@
 # One machine that becomes a mesh and then assigns itself plex's tool runtime.
 #
 # The audit-node bed proved an assigned *consumer* (novox/hq ADR 0048). This proves an assigned
-# module that *serves tools* (ADR 0052): the same first-node substrate, plus plex's tool runtime on
+# module that *serves tools* (ADR 0052): the same first-node foundation, plus plex's tool runtime on
 # top. The node enrols itself, the mesh issues plex a broker account scoped to serve.plex.* and
 # assigns it, the host runs the runtime container, and a caller invokes plex.plex_reachable over the
 # mesh — proof the module runs its own code as its own process under its own scoped account.
@@ -21,7 +21,7 @@ machines:
     cpus: 2
 
 images:
-  - mesh-control:development
+  - mesh-controller:development
   # Plex's tool runtime, built by scripts/build-module-runtime.sh plex into the local daemon and
   # loaded onto the machine, which holds it by its own image ID.
   - mesh-runtime-plex:development