Add two new test cases to verify preview path validation behavior on Windows:
1. `test_is_preview_path_allowed_case_insensitive_on_windows`: Ensures path validation is case-insensitive on Windows, addressing issues where drive letters and paths with different cases should match. This resolves GitHub issues #772 and #774.
2. `test_is_preview_path_allowed_rejects_prefix_without_separator`: Prevents false positives by ensuring paths are only allowed when they match the root path exactly followed by a separator, not just sharing a common prefix.
