feat(bonfire): add Passthrough and Long command fields

- Command.Passthrough turns off cobra flag parsing and uses arbitrary
  args, so every argument after the command name, including --help, -h
  and --, reaches Run through Input.Args unchanged
- Command.Long sets cobra's Long text for the help command; without it
  the description is shown as before
- both fields are additive: commands without Passthrough parse flags and
  reject unknown ones exactly as before
- README and docs/console/writing-commands.md describe both fields

modules/bonfire/command.go

@@ -15,6 +15,17 @@ 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 string
+	// Passthrough turns off flag parsing for the command: every argument
+	// after the command name, including --help, -h and --, reaches Run
+	// unchanged through Input.Args. Declared Flags are registered for the
+	// usage text only and are never parsed, so Input.Flag returns only
+	// their defaults. Declared Args shape the usage string but are not
+	// count-checked, so Input.Argument indexes the raw args. Passthrough
+	// suits wrapper commands that forward to another program.
+	Passthrough bool
 	Flags       []Flag
 	Args        []Arg
 	Run         func(ctx context.Context, in Input, out Output) error