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/identity/identity.go

@@ -19,7 +19,7 @@ import (
 	"time"
 
 	"github.com/jackc/pgx/v5"
-	"github.com/novox/mesh-control/internal/store"
+	"github.com/novox/mesh-controller/internal/store"
 )
 
 // Name is what this context is called: its database and its credential are named after it.

internal/identity/identity_test.go

@@ -13,7 +13,7 @@ import (
 	"time"
 
 	"github.com/jackc/pgx/v5"
-	"github.com/novox/mesh-control/internal/store"
+	"github.com/novox/mesh-controller/internal/store"
 )
 
 func fresh(t *testing.T) *Identity {