mesh-cli: the operator's command on every node, nox in zsh (hq ADR 0272)

The records send the operator to "the controller's terminal", and on the
control-node nothing answered (hq issue 343). mesh-cli is a module of its
own, assigned to every node and built from its own directory: its program
is unpacked into /usr/local/bin by an archive resource (one file, no link,
no copy), and its zsh contribution makes nox its alias. It holds no
credential: it asks the node-engine on its machine over the SDK's go/cli
socket, and prints the controller's answer with its exit.

The agent module's refusals and README, and the route adapter's README, now
name `mesh-cli settings set …` on the control-node instead of a
mesh-controller command nobody could type; a settings file is passed inline,
since a path would be read where the controller runs.

modules/mesh-cli/module.json

@@ -0,0 +1,31 @@
+{
+  "module": "mesh-cli",
+  "version": "1",
+  "resources": [
+    {
+      "id": "program",
+      "type": "archive",
+      "artifact": "program",
+      "path": "/usr/local/bin"
+    }
+  ],
+  "shell": [
+    {
+      "for": "zsh",
+      "slot": "normal",
+      "code": "# The operator's command (module mesh-cli, novox/hq ADR 0272): nox is mesh-cli, in interactive zsh only.\n# A script, sudo and a document meant to work everywhere say mesh-cli.\nalias nox=mesh-cli\n"
+    }
+  ],
+  "build": {
+    "artifacts": [
+      {
+        "name": "program",
+        "kind": "bundle",
+        "language": "go",
+        "system": "arch",
+        "from": "cmd/mesh-cli",
+        "binary": "mesh-cli"
+      }
+    ]
+  }
+}