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/postgres-node.yml

@@ -20,7 +20,7 @@ machines:
     cpus: 2
 
 images:
-  - mesh-control:development
+  - mesh-controller:development
   # postgres's runtime, built by scripts/build-module-runtime.sh postgres (it carries psql), loaded
   # onto the machine.
   - mesh-runtime-postgres:development