A definition names no host path for its own data

Twenty-eight modules' data directories are placed: the root as place ".", a sub-directory named by
its id, and every host-side reference — binds, secrets, own secrets, grants, receives, file paths,
mounts, env-files — as ${dir:<id>}. Resolved on the default root every path is the one the manifest
named before, which the controller's TestPlacedDirectoriesKeepTheirPaths proves over both checkouts;
so no data moves and no machine sees a change. Five directories whose id is not their last segment
keep their path as a placement (novox/hq issue 119, ADR 0112, design 27).

modules/hello-web/module.json

@@ -15,7 +15,7 @@
     }
   },
   "binds": {
-    "route": "/var/lib/hello-web/route.json"
+    "route": "${dir:state}/route.json"
   },
   "listens": [
     {
@@ -30,13 +30,13 @@
     {
       "id": "state",
       "type": "directory",
-      "path": "/var/lib/hello-web",
-      "mode": "0700"
+      "mode": "0700",
+      "place": "."
     },
     {
       "id": "page",
       "type": "file",
-      "path": "/var/lib/hello-web/index.html",
+      "path": "${dir:state}/index.html",
       "mode": "0644",
       "content": "hello from hello-web, routed by the mesh\n"
     },
@@ -54,7 +54,7 @@
         "8080"
       ],
       "volumes": [
-        "/var/lib/hello-web/index.html:/www/index.html:ro"
+        "${dir:state}/index.html:/www/index.html:ro"
       ],
       "args": [
         "sh",