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/enrol.go

@@ -13,7 +13,7 @@ import (
 
 // hereIs what `node list` says about a machine the mesh has heard from recently.
 //
-// mesh-control prints one of three words per node: "here", "never spoken", or "out of touch <age>".
+// mesh-controller prints one of three words per node: "here", "never spoken", or "out of touch <age>".
 // The installer waits for the first, and it is the only honest proof that the host agent is
 // running: an enrolled machine whose host is not running looks exactly like an enrolled machine
 // whose host has crashed, and both look exactly like a successful install until the first push