🧪 [testing] Add cache hit test for get_folder_id_by_name

[yj9404]

🎯 What: The get_folder_id_by_name function uses an internal cache (_FOLDER_CACHE) to avoid repeating API calls for folder lookups, but this logic was previously missing test coverage.
📊 Coverage: A new test test_get_folder_id_by_name_cache_hit was added which pre-populates the cache and asserts that requests.get is not called and the cached ID is returned correctly.
✨ Result: Test coverage improved by properly validating the in-memory cache functionality of get_folder_id_by_name, ensuring future refactoring won't regress this optimization.

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PR created automatically by Jules for task 11013813283074096124 started by @yj9404

[google-labs-jules]

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