feat(bonfire): Artisan help, examples, JSON listing and error hints

- help <command> and <command> --help print Description, Usage,
  Arguments, Options with defaults, Global options, Help and Examples
- Command.Examples and Command.Hidden (appended, additive); list --all
  shows hidden commands, list --format=json prints a bonfire.Listing
- CheckDocs reports commands lacking description, long help, examples or
  argument and option descriptions
- Error block with the ERROR badge, WithHint explanation and Try lines
  ({bin} replaced), cobra suggestions as Try, -v error chain, messages
  scrubbed by sunscreen; Reported errors print nothing and exit 1

modules/bonfire/command.go

@@ -15,8 +15,8 @@ var ErrCommandName = errors.New("bonfire: plugin command name must be namespace:
 type Command struct {
 	Name        string
 	Description string
-	// Long is optional extended help that cobra shows for the help command
-	// (help <command>). When empty, cobra falls back to Description.
+	// Long is optional extended help, shown under "Help:" by help
+	// <command> and <command> --help.
 	Long string
 	// Passthrough turns off flag parsing for the command: every argument
 	// after the command name, including --help, -h and --, reaches Run
@@ -29,6 +29,22 @@ type Command struct {
 	Flags       []Flag
 	Args        []Arg
 	Run         func(ctx context.Context, in Input, out Output) error
+	// Examples are shown under "Examples:" in the command's help and in
+	// the JSON listing, each as a "#" comment and the command line.
+	Examples []Example
+	// Hidden keeps a runnable command out of the list; list --all and the
+	// JSON listing still show it.
+	Hidden bool
+}
+
+// Example is one usage example of a command.
+type Example struct {
+	// Command is the command line without the binary, for example
+	// "admin:token:create jane --json"; help prints it after summer or
+	// bin/<name>.
+	Command string
+	// Description is a short sentence shown as a "#" comment above it.
+	Description string
 }
 
 // Flag describes a string flag passed to a command.