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

test/rebuild.test.ts

@@ -79,9 +79,9 @@ test("the whole-mesh bed hands its anchor no control-plane image", () => {
     ...Object.values(scenario.machines).flatMap((m) => m.images ?? []),
   ];
   assert.deepEqual(
-    named.filter((i) => i.startsWith("mesh-control")),
+    named.filter((i) => i.startsWith("mesh-controller")),
     [],
-    "the anchor is handed mesh-control, so genesis would never find out whether the installer " +
+    "the anchor is handed mesh-controller, so genesis would never find out whether the installer " +
       "really carries it",
   );
 });