fix(api-diff): strip class tags in type normalization to avoid false-positive diffs

[EspenAlbert]

Summary

Fix false-positive type-change diffs caused by <class '...'> tags in type annotations.

Some Python introspection paths produce type strings wrapped in <class 'module.Name'> (e.g., from repr() of type objects). These were not normalized before comparison, causing normalize_type to report spurious PARAM_TYPE_CHANGED diffs when comparing baseline and dev API dumps.

The fix strips <class '...'> tags before applying qualified-name normalization, so <class 'ask_shell._internal.models.ShellRun'> correctly matches ShellRun.

[codecov-commenter]

Codecov Report

❌ Patch coverage is 94.11765% with 3 lines in your changes missing coverage. Please review.
✅ Project coverage is 79.99%. Comparing base (a6fcde9) to head (3395795).
⚠️ Report is 5 commits behind head on main.

Files with missing lines	Patch %	Lines
pkg_ext/_internal/api_diff.py	93.75%	3 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #23      +/-   ##
==========================================
+ Coverage   79.87%   79.99%   +0.11%     
==========================================
  Files          80       80              
  Lines        4990     5033      +43     
==========================================
+ Hits         3986     4026      +40     
- Misses       1004     1007       +3     

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