The previous method for detecting FAT filesystems on macOS relied on parsing `df` and `mount` command output, which is brittle and prone to issues with command output variations.
This change replaces the shell command parsing with a more robust and idiomatic approach using Foundation.framework's `NSURL` API. This directly queries the volume's localized format description, ensuring accurate identification of MS-DOS (FAT12/FAT16/FAT32) volumes while correctly distinguishing them from ExFAT.
Adds unit tests for the `isFAT` function to verify basic functionality and error handling.
Closes#3483
