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/inventory/migrations/0017-what-a-machine-already-holds.sql

@@ -1,6 +1,6 @@
 -- Ports a machine holds that the mesh did not assign.
 --
--- novox/hq ADR 0038. The substrate is not a module: a node raises it from the bundle it carries
+-- novox/hq ADR 0038. The foundation is not a module: a node raises it from the bundle it carries
 -- before any mesh exists, so the control plane has never heard of the store or the broker. Told
 -- what they hold, it can put a module somewhere else; not told, it hands out a port one of them
 -- has and finds out from a container runtime three layers down.