Enforce keyword-only arguments in make_image_file

[adamtheturtle]

Summary

• Add * to make_image_file in tests/mock_vws/utils/__init__.py to enforce keyword-only arguments, consistent with the project's conventions.
• All existing call sites already use keyword arguments, so no other changes are needed.

Test plan

• All pre-commit hooks pass.
• Existing tests are unaffected since all callers already use keyword arguments.

Made with Cursor

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Note

Low Risk
Small, test-only API tightening; risk is limited to breaking any unseen positional call sites.

Overview
Updates the test helper make_image_file to enforce keyword-only parameters by adding a * to its signature, preventing positional-argument usage and aligning with project conventions.

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