List every module's preferences in the settings verb (hq ADR 0262)

One verb is the interface to every preference, so no module builds a settings tool of its own: each
key, its default and why, and every assigned machine's value with its source.

internal/catalogue/verbs.go

@@ -251,19 +251,22 @@ var ControllerVerbs = []Verb{
 	{Name: "settings", Description: "Read or set what an assignment is configured with: a module's settings for the whole " +
 		"mesh, or for one machine. Without values or clear, answers the layer as it stands — read it before setting it — " +
 		"then every value the module gives a default or a layer sets, with where it comes from: the module's default, " +
-		"the mesh, or the machine (novox/hq ADR 0262); " +
+		"the mesh, or the machine (novox/hq ADR 0262); with list \"preferences\", or with no module, every " +
+		"module's preferences and each machine's value; " +
 		"with history, the layers it replaced. Setting replaces that layer whole and answers each key it adds (+), " +
 		"changes (~) and removes (-); a set that would remove a key is refused unless replace says it is meant " +
 		"(novox/hq ADR 0217). Takes effect at the next push. With clear, removes the layer and the module is back to " +
 		"what its definition says; a cleared or replaced layer is kept in the history.",
 		Input: schema(map[string]string{
-			"module":  "the module's name",
+			"module":  "the module's name; with list, only that module's",
 			"values":  "the settings as a JSON object, for set",
 			"node":    "one machine; the whole mesh when absent",
 			"clear":   "\"true\" to remove the layer instead of setting it; not with values",
 			"replace": "\"true\": with values, the set is meant to remove the keys the layer had and it does not name",
 			"history": "\"true\": without values or clear, the layers this one replaced, the latest first",
-		}, []string{"module"}, "clear", "replace", "history")},
+			"list": "\"preferences\": every module's preferences — key, default and why — and the value on each " +
+				"machine it is assigned to with where it comes from; module and node narrow it (novox/hq ADR 0262)",
+		}, nil, "clear", "replace", "history")},
 	{Name: "command", Description: "Run one command line of the controller's own, as you would type it at its " +
 		"shell — `node account g14 jochen`, `node show ace`, `module list` — and answer what it printed. The " +
 		"generic verb beside the named ones (novox/hq ADR 0154): everything the binary can do, without a verb " +