Add minimal Hello World Python entrypoint

[Copilot]

This change adds a basic runnable Hello World implementation to the repository so it can be used for simple testing. It also documents the expected invocation in the existing README.

• Hello World entrypoint

  • Adds hello_world.py with a minimal executable script
  • Exposes the output through a small get_message() function and prints it when run directly

• Usage documentation

  • Updates README.md with the command to run the script

def get_message():
    return "Hello, World!"


if __name__ == "__main__":
    print(get_message())

Original prompt

Build a basic Hello World code for testing