Fix type safety hack in memoization test

[google-labs-jules]

Updated the trackingExecute function in src/runner/memoization.test.ts to accept the required arguments (step, context, executeStepFn) and optional arguments. This aligns the function signature with the expected executeLlmStep type, resolving the type error that previously required a @ts-ignore comment. This change improves type safety and removes technical debt in the test suite.

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PR created automatically by Jules for task 14701563604613585281 started by @mhingston

[google-labs-jules]

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