fix: clean up event listeners and timers in React hooks

[atomantic]

Better Audit — Stack-Specific (React)

2 findings fixed across 2 files. Added removeEventListener cleanup in useSSE hook (memory leak fix). Added setTimeout cleanup in CopyButton.

[Copilot]

Pull request overview

This PR fixes two memory-leak-related cleanup issues in React hooks/components. In useSSE.ts, named SSE event listeners are now properly tracked and removed via removeEventListener before the EventSource is closed. In CopyButton.tsx, a useRef holds the debounce timer ID so it can be cleared both when a new copy action fires and when the component unmounts.

Changes:

• Introduced a listeners array in useSSE.ts to track and explicitly remove named event listeners in the effect cleanup.
• Added useRef + useEffect in CopyButton.tsx to cancel any pending setTimeout on unmount, preventing a state update on an unmounted component.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
client/src/hooks/useSSE.ts	Tracks named event listeners and calls removeEventListener for each before closing the EventSource.
client/src/components/ui/CopyButton.tsx	Stores the setTimeout handle in a ref so it can be cancelled both on subsequent copies and on unmount.

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