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/link/enrol_shape_test.go

@@ -11,9 +11,9 @@ import (
 
 	"golang.org/x/crypto/nacl/box"
 
-	"github.com/novox/mesh-control/internal/catalogue"
-	"github.com/novox/mesh-control/internal/inventory"
-	"github.com/novox/mesh-control/internal/link"
+	"github.com/novox/mesh-controller/internal/catalogue"
+	"github.com/novox/mesh-controller/internal/inventory"
+	"github.com/novox/mesh-controller/internal/link"
 )
 
 // What a node says when it joins, as that node's own code writes it.
@@ -25,7 +25,7 @@ import (
 // Skipped unless MESH_ENROL names the file the host's suite wrote:
 //
 //	mesh-host:    MESH_ENROL_OUT=/tmp/enrol.json go test ./internal/link/
-//	mesh-control: MESH_ENROL=/tmp/enrol.json make check
+//	mesh-controller: MESH_ENROL=/tmp/enrol.json make check
 //
 // **What this does not cover**, said so nobody reads more into a pass than is there: the full
 // enrolment path also issues a broker account, and that needs a broker. What is checked here is