feat: improve input handling

- Add support for 'quit' command alongside 'exit'

- Update input prompt to show both exit options

- Enhance empty input handling to catch both empty strings and whitespace

- Replace isspace() check with more robust empty string validation

- Optimize command checking by storing lowercase result

- Improve code readability and user experience

main.py

@@ -8,11 +8,12 @@ async def main():
     agent = Manus()
     while True:
         try:
-            prompt = input("Enter your prompt (or 'exit' to quit): ")
-            if prompt.lower() == "exit":
+            prompt = input("Enter your prompt (or 'exit'/'quit' to quit): ")
+            prompt_lower = prompt.lower()
+            if prompt_lower in ["exit", "quit"]:
                 logger.info("Goodbye!")
                 break
-            if prompt.strip().isspace():
+            if not prompt.strip():
                 logger.warning("Skipping empty prompt.")
                 continue
             logger.warning("Processing your request...")