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

Dockerfile

@@ -22,13 +22,13 @@ COPY . .
 ARG VERSION=development
 RUN CGO_ENABLED=0 go build -trimpath \
         -ldflags "-s -w -X main.version=${VERSION}" \
-        -o /mesh-control ./cmd/mesh-control
+        -o /mesh-controller ./cmd/mesh-controller
 
 FROM scratch
-COPY --from=build /mesh-control /mesh-control
+COPY --from=build /mesh-controller /mesh-controller
 
 # Numeric because there is no /etc/passwd to look a name up in. Nothing here needs to be root:
 # it opens outbound connections and writes nothing to its own filesystem.
 USER 65534:65534
 
-ENTRYPOINT ["/mesh-control"]
+ENTRYPOINT ["/mesh-controller"]