fix(renderer): cancel copied prompt reset on unmount (#20906)

* fix(renderer): cancel copied prompt reset on unmount

* fix: address memory PR review regressions and withdraw false positives

---------

Co-authored-by: m4air <m4air@Mac.localdomain>
Co-authored-by: m4air <m4air@m4airs-MacBook-Air.local>

src/renderer/src/components/settings/EphemeralVmsPane.test.tsx

@@ -138,6 +138,51 @@ describe('EphemeralVmsPane', () => {
     })
   })
 
+  it('does not schedule a reset when clipboard completion arrives after unmount', async () => {
+    let finishClipboard!: () => void
+    vi.mocked(window.api.ui.writeClipboardText).mockReturnValueOnce(
+      new Promise<void>((resolve) => {
+        finishClipboard = resolve
+      })
+    )
+    const container = await renderPane()
+    const setTimeout = vi.spyOn(window, 'setTimeout')
+    try {
+      await act(async () => {
+        container.querySelector<HTMLButtonElement>('button[aria-label="Copy"]')?.click()
+      })
+      await act(async () => roots.pop()?.unmount())
+      setTimeout.mockClear()
+      await act(async () => {
+        finishClipboard()
+        await Promise.resolve()
+      })
+      expect(setTimeout.mock.calls.filter(([, delay]) => delay === 1500)).toHaveLength(0)
+    } finally {
+      setTimeout.mockRestore()
+    }
+  })
+
+  it('shows copied feedback while mounted and releases its reset on unmount', async () => {
+    const container = await renderPane()
+    const setTimeout = vi.spyOn(window, 'setTimeout')
+    const clearTimeout = vi.spyOn(window, 'clearTimeout')
+    try {
+      await act(async () => {
+        container.querySelector<HTMLButtonElement>('button[aria-label="Copy"]')?.click()
+      })
+      expect(container.querySelector('button[aria-label="Copy"]')?.textContent).toBe('Copied')
+      const timerIndex = setTimeout.mock.calls.findIndex(([, delay]) => delay === 1500)
+      expect(timerIndex).toBeGreaterThanOrEqual(0)
+      const timer = setTimeout.mock.results[timerIndex].value
+      await act(async () => roots.pop()?.unmount())
+      expect(clearTimeout).toHaveBeenCalledWith(timer)
+    } finally {
+      setTimeout.mockRestore()
+      clearTimeout.mockRestore()
+    }
+  })
+
   it('refreshes the catalog when plugin content changes', async () => {
     const listRecipeCatalog = window.api.ephemeralVm.listRecipeCatalog as ReturnType<typeof vi.fn>
     const container = await renderPane()

src/renderer/src/components/settings/EphemeralVmsPane.tsx

@@ -45,6 +45,15 @@ export function EphemeralVmsPane(): React.JSX.Element {
   const [promptCopied, setPromptCopied] = useState(false)
   const mountedRef = useMountedRef()
   const refreshGenerationRef = useRef(0)
+  const promptResetTimerRef = useRef<number | null>(null)
+
+  useEffect(() => {
+    return () => {
+      if (promptResetTimerRef.current !== null) {
+        window.clearTimeout(promptResetTimerRef.current)
+      }
+    }
+  }, [])
 
   // Why: an absent runtime still resolves to the local host, which is what the
   // seven sibling panes rely on to reach the Windows npx preflight.
@@ -126,8 +135,17 @@ export function EphemeralVmsPane(): React.JSX.Element {
     try {
       await window.api.ui.writeClipboardText(AGENT_PROMPT)
       useAppStore.getState().recordFeatureInteraction('ephemeral-vm-setup')
+      if (!mountedRef.current) {
+        return
+      }
       setPromptCopied(true)
-      setTimeout(() => setPromptCopied(false), 1500)
+      if (promptResetTimerRef.current !== null) {
+        window.clearTimeout(promptResetTimerRef.current)
+      }
+      promptResetTimerRef.current = window.setTimeout(() => {
+        promptResetTimerRef.current = null
+        setPromptCopied(false)
+      }, 1500)
     } catch {
       toast.error(
         translate(