The controller seat gains a generic verb: command runs one line of the binary and answers what it printed

Beside the named verbs, `command` takes a command line as the controller's
own shell would — `node account g14 jochen`, `node show ace`, `module list` —
splits it as a shell does (quotes group, backslash escapes, nothing expanded)
and runs it in this binary like every other verb. The named verbs keep their
schemas; this is the whole binary, added because the operator decided any
node may call any tool (hq ADR 0175) and a verb per command was the only
thing keeping the rest behind a shell on the control node. ADR 0154 carries
the dated note. Tests: a plain line, quoted words, an empty line and an
unclosed quote refused.

cmd/mesh-controller/seatverbs_test.go

@@ -171,3 +171,27 @@ func TestAJSONVerbsAnswerIsItsStandardOutput(t *testing.T) {
 		t.Fatalf("stderr and stdout are both what the command said: %s", answer.Output)
 	}
 }
+
+// `command` is the generic verb: the command line as given, split as a shell would, nothing added —
+// so an operator's `node account g14 jochen` is one call through the console rather than a shell on
+// the control node (novox/hq ADR 0154, ADR 0175).
+func TestCommandRunsTheLineAsGiven(t *testing.T) {
+	argv, err := argvFor("command", map[string]any{"command": "node account g14 jochen"})
+	if err != nil || strings.Join(argv, " ") != "node account g14 jochen" {
+		t.Fatalf("a plain line: %v %v", argv, err)
+	}
+	argv, err = argvFor("command", map[string]any{"command": `settings set dnsmasq '{"a": "b c"}' --node ace`})
+	if err != nil || len(argv) != 6 || argv[3] != `{"a": "b c"}` {
+		t.Fatalf("a quoted word stays one word: %q %v", argv, err)
+	}
+	argv, err = argvFor("command", map[string]any{"command": `node add "the box" --adopted`})
+	if err != nil || len(argv) != 4 || argv[2] != "the box" {
+		t.Fatalf("double quotes group: %q %v", argv, err)
+	}
+	if _, err := argvFor("command", map[string]any{"command": "   "}); err == nil {
+		t.Fatal("an empty line was accepted")
+	}
+	if _, err := argvFor("command", map[string]any{"command": `node "unclosed`}); err == nil {
+		t.Fatal("an unclosed quote was accepted")
+	}
+}