Expansion import resolution collides on duplicate module filenames

[drogers0]

Summary

Call expansion can resolve imports to the wrong module when multiple files share the same name/stem.

Affected code

• src/clonehunter/snippets/expansion.py:251
• src/clonehunter/snippets/expansion.py:530

Problem

_module_name_map indexes modules by path.name and path.stem, which collides for files like:

• pkg1/util.py
• pkg2/util.py

This can cause expansion to attach helper code from the wrong module.

Expected

Use a collision-safe module identity (fully qualified module path / repo-relative path mapping) so import resolution is deterministic and correct.