node list and module list answer --json, and the nodes and modules verbs use it (hq ADR 0195)

The console's discovery reads the machines and the modules; parsing a printed column breaks when it
is reworded. Both now answer JSON on --json, as status and seats do, and the seat verbs ask for it.

cmd/mesh-controller/nodes.go

@@ -2,6 +2,7 @@ package main
 
 import (
 	"context"
+	"encoding/json"
 	"errors"
 	"flag"
 	"fmt"
@@ -44,6 +45,21 @@ func nodeCommand(ctx context.Context, args []string) error {
 		if err != nil {
 			return err
 		}
+		// **The same list, for something other than a person** — the console's discovery reads it
+		// (novox/hq ADR 0195), and a reader that parses a printed column breaks when it is reworded.
+		if len(args) > 1 && args[1] == "--json" {
+			type listed struct {
+				Name  string `json:"name"`
+				Heard string `json:"heard"`
+				Mode  string `json:"mode"`
+				ID    string `json:"id"`
+			}
+			out := make([]listed, 0, len(nodes))
+			for _, n := range nodes {
+				out = append(out, listed{Name: n.Name, Heard: heardFrom(n), Mode: modeOf(n), ID: n.ID})
+			}
+			return printJSON(out)
+		}
 		if len(nodes) == 0 {
 			// Said rather than printed as nothing: an empty list and a failed read must never
 			// look the same, and this command answering "none" is only honest because getting
@@ -500,3 +516,13 @@ func orNotReported(s string) string {
 	}
 	return s
 }
+
+// printJSON prints a value as indented JSON, the shape every `--json` answers in.
+func printJSON(v any) error {
+	body, err := json.MarshalIndent(v, "", "  ")
+	if err != nil {
+		return err
+	}
+	fmt.Println(string(body))
+	return nil
+}