🧪 Add missing tests for expectBoolean validation helper

[akutuva21]

🎯 What: Added missing tests for the expectBoolean validation helper in tests/validate-metadata.test.js.
📊 Coverage: Covered happy paths (boolean true and false) and various edge cases and error conditions (null, undefined, number, string, object, empty string) to ensure correct error reporting.
✨ Result: Improved test coverage and reliability of the validate-metadata.js script.

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PR created automatically by Jules for task 8497813441427237446 started by @akutuva21

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