Exercise 2: Why the Cleanup Function's Track-Stopping Line Matters — Possible Solution
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WHAT HAPPENS IF THAT LINE IS OMITTED
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Without stream?.getTracks().forEach(track => track.stop()) in the cleanup function, the camera stream keeps running even after the component that started it unmounts. getUserMedia's own stream isn't automatically released just because the React component that requested it is gone - something has to explicitly call stop() on each track, and the cleanup function is the only place that happens.

WHY THIS MATTERS SPECIFICALLY FOR A SCAN SCREEN
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A scan screen is exactly the kind of component a user navigates to and away from repeatedly - scan an item, go back, scan another later. Each mount without a matching cleanup leaves one more orphaned camera stream running in the background. Beyond draining battery and leaving the camera's "in use" indicator lit when it shouldn't be, repeated visits can eventually hit the browser's own limit on simultaneous open camera streams, causing a later getUserMedia call to fail outright for a reason that would look confusing without knowing about the leaked streams underneath.

WHY THIS WORKS AS AN ANSWER
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It correctly explains that a camera stream isn't automatically released on unmount and requires an explicit stop() call, and correctly connects that specifically to a scan screen's own repeated mount/unmount pattern, naming concrete consequences (battery drain, a stuck camera indicator, eventually failing getUserMedia calls).