fix: avoid splitting .zipx paths as zip files

[leno23]

Summary

• Avoid treating directory names like .zipx as zip archive boundaries during path normalization.
• Keep the existing .zip, .egg, and .egg! archive path handling for actual archive-style inner paths.
• Add a focused regression test for an existing file under a .zipx/ directory.

Related Issues / Closes

Closes #265

Testing

• Added the regression first and verified it failed before the source change: _apply_func_and_normalize_case returned .zip/x/main.py instead of .zipx/main.py.
• python3 -m pytest tests_python/test_pydevd_file_utils.py -q — passed
• python3 -m py_compile pydevd_file_utils.py tests_python/test_pydevd_file_utils.py — passed
• git diff --check — passed
• Also tried python3 -m pytest tests_python/test_debugger.py::test_debug_zip_files -q; a baseline run without this source change failed in this environment because the test dependency untangle is not installed, so this broader debugger integration test was not usable as validation here.

AI assistance disclosure

This draft PR was prepared by Hermes Agent as an automated maintainer-assist change. A human maintainer should review before marking ready or merging.