feat: Allow starting CLI without initial prompt (#2)

Make the initial prompt optional. When no arguments are provided,
the CLI now goes directly to interactive mode instead of exiting.

Co-authored-by: Claude Opus 4.5 <noreply@anthropic.com>

main.go

@@ -178,12 +178,8 @@ func main() {
 		logFilePath = filepath.Join(stateDir, "klod", "sessions", sessionTime+".log")
 	}
 
-	// Get initial prompt from command-line arguments
-	if len(os.Args) < 2 {
-		fmt.Fprintln(os.Stderr, "Usage: klod <your prompt>")
-		os.Exit(1)
-	}
-
+	// Get initial prompt from command-line arguments (if provided)
+	if len(os.Args) >= 2 {
 		initialPrompt := strings.Join(os.Args[1:], " ")
 
 		// Add initial user message to conversation history
@@ -211,6 +207,7 @@ func main() {
 		}
 		conversationHistory = append(conversationHistory, assistantMsg)
 		logConversation(assistantMsg)
+	}
 
 	// Interactive conversation loop
 	reader := bufio.NewReader(os.Stdin)