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

internal/declaration/declaration.go

@@ -1076,7 +1076,7 @@ func vocabulary() string {
 // ParseFileTrusted reads a declaration from a file somebody handed this host.
 //
 // The same as ParseTrusted, and it allows whole-line `//` comments first. A pinned, hand-authored
-// artefact that nobody can annotate is one nobody can review — the substrate bundle is mostly
+// artefact that nobody can annotate is one nobody can review — the foundation bundle is mostly
 // explanation of why each digest is what it is.
 //
 // **Only for a file, never for the link.** Over the link the format stays exactly JSON, because