🧪 Add tests for validate_examples.py

[edithatogo]

🎯 What: The testing gap addressed
The main function in validate_examples.py and some branches of validate_example_corpus were missing explicit tests, particularly for the console output in failure conditions and the fallback sys.argv usage.

📊 Coverage: What scenarios are now tested
Added missing branch and statement coverage for main, achieving 100% coverage on validate_examples.py.
Tested argv=None to ensure fallback.
Tested validation output when invalid examples are supplied and when valid examples are unexpectedly invalid.

✨ Result: The improvement in test coverage
validate_examples.py is now fully tested, ensuring deterministic validation of PIC examples without silent regressions.

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PR created automatically by Jules for task 12760805854109482263 started by @edithatogo

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