fix(install-e2e): release inherited pipes after launcher exit

tests-js/install-process-close.test.ts

@@ -6,11 +6,14 @@ import { expect, it, vi } from 'vitest'
 const { observeProcessClose } = createRequire(import.meta.url)('../tests/install/e2e-assets/process-close.cjs')
 
 it('waits for native close, not exit, and retains a close observed before hand-off', async () => {
-  const child = new EventEmitter()
+  const pipe = { destroy: vi.fn() }
+  const child = Object.assign(new EventEmitter(), { stdio: [null, pipe], exitCode: null, signalCode: null })
   const waitForClose = observeProcessClose(child)
+  expect(pipe.destroy).not.toHaveBeenCalled()
   let finished = false
   const completion = waitForClose().then(() => { finished = true })
   child.emit('exit', 0)
+  expect(pipe.destroy).toHaveBeenCalledOnce()
   await Promise.resolve()
   expect(finished).toBe(false)
   child.emit('close', 0)
@@ -22,7 +25,7 @@ it('waits for native close, not exit, and retains a close observed before hand-o
 it('fails if the launched process never closes', async () => {
   vi.useFakeTimers()
   try {
-    const waitForClose = observeProcessClose(new EventEmitter())
+    const waitForClose = observeProcessClose(Object.assign(new EventEmitter(), { stdio: [], exitCode: null, signalCode: null }))
     const completion = expect(waitForClose(2_000)).rejects.toThrow('Electron process did not close')
     await vi.advanceTimersByTimeAsync(2_000)
     await completion

tests/install/e2e-assets/process-close.cjs

@@ -6,6 +6,13 @@ function observeProcessClose(child) {
     closed = true
     resolve()
   }))
+  // Windows descendants can inherit pipe handles and postpone 'close' after
+  // the launch process exits. Release our handles, never kill descendants.
+  const releasePipes = () => {
+    for (const stream of child.stdio) stream?.destroy()
+  }
+  child.once('exit', releasePipes)
+  if (child.exitCode !== null || child.signalCode !== null) releasePipes()
   return async function waitForClose(timeoutMs = 120_000) {
     if (closed) return
     let timer