Address PR review comments: fix UNC path handling, improve test coverage, remove problematic test files

- Fixed UNC path handling bug in normalizePath function to preserve leading double backslashes
- Added comprehensive test coverage for drive letter capitalization and UNC paths
- Removed file-operations.test.ts and core-functionality.test.ts as they were testing their own code rather than actual server functionality
- All path-utils tests now pass with 100% coverage of the actual utility functions

Author: olaservo