Change in Code Structure for better management and error handling

[Aksh8t]

Key Changes :

Encapsulation in QwenChatDemo Class: Most of the logic is encapsulated in the QwenChatDemo class. This allows easy testing, better organization, and clearer state management.

Clearer Separation of Concerns: The code is cleaner with input handling, chat logic, and command execution separated.

Error Handling: Improved error handling for user inputs and commands, ensuring the application handles edge cases better.

Code Readability: Functions are more modular, each handling a specific task (such as command handling or model loading).

Extensibility: By encapsulating the functionality into a class, you can more easily extend or modify features in the future (e.g., adding more commands or model configurations).