feat: implement CLI support for metadata display (Phase 4)

internal/cli/flags.go

@@ -104,6 +104,7 @@ type Flags struct {
 	Notification                    bool                 `long:"notification" yaml:"notification" description:"Send desktop notification when command completes"`
 	NotificationCommand             string               `long:"notification-command" yaml:"notificationCommand" description:"Custom command to run for notifications (overrides built-in notifications)"`
 	Thinking                        domain.ThinkingLevel `long:"thinking" yaml:"thinking" description:"Set reasoning/thinking level (e.g., off, low, medium, high, or numeric tokens for Anthropic or Google Gemini)"`
+	ShowMetadata                    bool                 `long:"show-metadata" description:"Print metadata to stderr"`
 	Debug                           int                  `long:"debug" description:"Set debug level (0=off, 1=basic, 2=detailed, 3=trace)" default:"0"`
 }
 
@@ -459,6 +460,7 @@ func (o *Flags) BuildChatOptions() (ret *domain.ChatOptions, err error) {
 		Voice:               o.Voice,
 		Notification:        o.Notification || o.NotificationCommand != "",
 		NotificationCommand: o.NotificationCommand,
+		ShowMetadata:        o.ShowMetadata,
 	}
 	return
 }

internal/core/chatter.go

@@ -85,9 +85,12 @@ func (o *Chatter) Send(request *domain.ChatRequest, opts *domain.ChatOptions) (s
 					printedStream = true
 				}
 			case domain.StreamTypeUsage:
-				// Placeholder for metadata handling
-				// Future logic: Store usage in session or context
+				if opts.ShowMetadata && update.Usage != nil {
+					fmt.Fprintf(os.Stderr, "\n[Metadata] Input: %d | Output: %d | Total: %d\n",
+						update.Usage.InputTokens, update.Usage.OutputTokens, update.Usage.TotalTokens)
+				}
 			case domain.StreamTypeError:
+				fmt.Fprintf(os.Stderr, "Error: %s\n", update.Content)
 				errChan <- errors.New(update.Content)
 			}
 		}

internal/domain/domain.go

@@ -51,6 +51,7 @@ type ChatOptions struct {
 	Voice               string
 	Notification        bool
 	NotificationCommand string
+	ShowMetadata        bool
 }
 
 // NormalizeMessages remove empty messages and ensure messages order user-assist-user