Add CLI runner for QuestioningEngine

[Chengyue5211]

Motivation

• Make the QuestioningEngine runnable as a simple interactive CLI so the finite-state behavior can be exercised directly from the module.
• Treat EOF and empty input as valid stop signals so the CLI can exit cleanly in non-interactive contexts.

Description

• Add a _run_cli() function that instantiates QuestioningEngine, prints engine.start(), then loops reading user input and printing engine.handle_input(...) until the engine reaches State.EXIT.
• Add a module entry point if __name__ == "__main__": _run_cli() so the file can be executed with python questioning_engine.py.
• Handle EOFError by treating it as an empty input string which the engine treats as an exit condition.

Testing

• No automated tests were run for this change.

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Codex Task