Cart Management

This skill appears to be what it says (React cart patterns) and has no unusual external requirements. Before using the suggested code: 1) Fix the stale-state bug — compute the new cart from the previous state and then persist that new value to localStorage (use functional updates and write the same new object to storage). 2) Avoid duplicating derived state (keep product IDs derived from cart items, or ensure both are updated atomically). 3) Guard localStorage usage for server-side rendering (check for window) and wrap JSON.parse in try/catch. 4) Remember localStorage is readable by any page script — do not store secrets or sensitive info there (XSS risk). 5) Consider debouncing or batching persistence to reduce writes and handle concurrent updates safely. These are implementation-quality and security-adjacent issues, not signs of malicious behavior.