🧪 [testing improvement] Add tests for zip_dir

[Tcode-Motion]

🎯 What: Added tests for zip_dir in stdlib/src/compress.rs.
📊 Coverage: Covered happy path for directory compression, and error conditions for invalid source directories.
✨ Result: Improved test coverage and reliability for filesystem compression functions.

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PR created automatically by Jules for task 9038664599961891736 started by @Tcode-Motion

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