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/bootstrap/module.go

@@ -80,7 +80,7 @@ func installModule(ctx context.Context, o Options, control controlPlane, module
 // Split out because one module needs something in between: the control plane's own store
 // connections have to be accepted before its declaration is composed, or the mesh would seal
 // thirty-two random bytes into the file it expects a connection string in and the container would
-// come up unable to open anything (mesh-control's `secret accept`, and what it exists for).
+// come up unable to open anything (mesh-controller's `secret accept`, and what it exists for).
 //
 // **`module add` is run every time and is not skipped when the module is already known.** It is an
 // upsert on the manifest, and the manifest is exactly what changes between runs — step 9 registers