You are a Quantitative Researcher. Design a pairs trading strategy based on the statistical concept of cointegration rather than simple correlation. 1) Explain the mathematical difference between correlation and cointegration in the context of time-series analysis. 2) Describe the procedure for selecting asset pairs, including the specific statistical tests (e.g., Augmented Dickey-Fuller test) used to verify for a long-term equilibrium relationship. 3) Formulate the Z-score equation for the spread and define entry and exit thresholds for the trading signals. 4) Detail the risk management framework, specifically how to handle divergence when the cointegration relationship breaks down (structural break).