PR Summary:

• Fixes a bug in _ensure_path_registered where the OS-normalized path (norm_dest) was incorrectly persisted to config instead of the original user-provided path (dest_path).
• Adds diagnostic logging to _merge_publish_into_bin in the build tooling to surface file overwrites during publish merges.

Review Summary:

Both changes are clean, minimal, and correct. The core fix in script.py addresses a real subtle bug: os.path.normcase lowercases paths on Windows (e.g. C:\Users\MyExt → c:\users\myext), so persisting norm_dest would store a mangled path in user config. Using norm_dest only for comparison (line 64) while storing the original dest_path (line 66) is the right pattern. The _labs.py change is purely informational build-time logging with no side effects. All code in script.py correctly targets IronPython 2.7 (.format() strings, no f-strings), consistent with repository standards.

Suggestions

• Add a unit test for _ensure_path_registered verifying that the original path (not the normalized form) is saved to config. Apply
• Audit other callers of set_thirdparty_ext_root_dirs to ensure none of them similarly persist normalized paths instead of original user paths. Apply