🧪 Add tests for isCollectionEntry in generate-manifest.js

[akutuva21]

🎯 What: The testing gap addressed is the lack of unit tests for the isCollectionEntry function in scripts/generate-manifest.js.
📊 Coverage: The new tests cover scenarios where the metadata has a valid collection property, when it is missing completely, and when it is set to falsy values like null or undefined.
✨ Result: Test coverage for generate-manifest.js has been improved, providing a safety net for future refactoring of this core function.

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PR created automatically by Jules for task 17901415298177206964 started by @akutuva21

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