Enforce keyword-only arguments in test helper

[adamtheturtle]

Summary

• Add * to _wait_for_target_processed in tests/mock_vws/fixtures/prepared_requests.py to enforce keyword-only arguments, preventing accidental positional usage
• All existing call sites already use keyword arguments, so this is a non-breaking change

Test plan

• Verify existing tests pass (all callers already use keyword args)

Made with Cursor

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Note

Low Risk
Tiny signature tightening in test-only code; all current call sites already use keywords so impact should be minimal.

Overview
Enforces keyword-only arguments for the test helper _wait_for_target_processed in tests/mock_vws/fixtures/prepared_requests.py by adding * to its signature, preventing accidental positional calls.

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