Keep places and accesses at the terminal, and refuse a line break in any setting

Through the settings verb, or a settings line run by the generic command
verb, any caller of the mesh's console could place a module's directory at
/etc with an owner of its own and have the node-engine, as root, hand it
over at the next push, or mount any of the machine's paths into a container
(hq issue 339). A change to either key is now refused in every process a
verb runs, the generic verb refuses settings writes outright, and neither key
may name the machine's own trees from anywhere, the terminal included. A
line break, carriage return or NUL in any setting, which a file it is
written into reads as a line of the caller's own, is refused where a layer
is kept and where it is composed; PEM blocks alone may hold lines.

cmd/mesh-controller/seatverbs.go

@@ -245,6 +245,14 @@ func (a *verbArguments) commandLine() ([]string, error) {
 		if len(argv) == 0 {
 			return nil, errors.New("command names no command")
 		}
+		// A layer is written through the settings verb, never the generic one (novox/hq issue 339): the
+		// settings verb is where what a verb may not set is refused, and one route is one set of words.
+		// The command refuses places and accesses through any verb as well; this says so before it runs.
+		if argv[0] == "settings" && slices.ContainsFunc(argv[1:], func(w string) bool { return w == "set" || w == "clear" }) {
+			return nil, errors.New("settings are set and cleared through the settings verb, not the generic " +
+				"command; and places and accesses only at the controller's terminal (novox/hq issue 339). " +
+				"Nothing was done")
+		}
 		// The generic verb is no way round the hand-act log (novox/hq to-be 45 §7): a repair through
 		// it says why, as it would through its own verb.
 		if repair := repairingCommand(argv); repair != "" && !slices.ContainsFunc(argv, isWhyFlag) {