add partials vs kwargs test for clarity

[TimMonko]

This pull request adds a new test to demonstrate and recommend using keyword arguments (kwargs) as a cleaner alternative to functools.partial when passing extra arguments to batch processing functions. This helps clarify best practices for writing batch tests and ensures both approaches produce identical results.

Testing improvements:

• Added test_kwargs_replaces_partial to tests/test_runner.py to demonstrate and recommend using kwargs instead of functools.partial for passing extra arguments to batch functions. The test confirms that both approaches yield the same results, but highlights kwargs as the cleaner pattern.