fix(sdk): handle Windows opencode spawn and shutdown (#20772)

packages/sdk/js/src/process.ts

@@ -0,0 +1,31 @@
+import { type ChildProcess, spawnSync } from "node:child_process"
+
+// Duplicated from `packages/opencode/src/util/process.ts` because the SDK cannot
+// import `opencode` without creating a cycle (`opencode` depends on `@opencode-ai/sdk`).
+export function stop(proc: ChildProcess) {
+  if (proc.exitCode !== null || proc.signalCode !== null) return
+  if (process.platform === "win32" && proc.pid) {
+    const out = spawnSync("taskkill", ["/pid", String(proc.pid), "/T", "/F"], { windowsHide: true })
+    if (!out.error && out.status === 0) return
+  }
+  proc.kill()
+}
+
+export function bindAbort(proc: ChildProcess, signal?: AbortSignal, onAbort?: () => void) {
+  if (!signal) return () => {}
+  const abort = () => {
+    clear()
+    stop(proc)
+    onAbort?.()
+  }
+  const clear = () => {
+    signal.removeEventListener("abort", abort)
+    proc.off("exit", clear)
+    proc.off("error", clear)
+  }
+  signal.addEventListener("abort", abort, { once: true })
+  proc.on("exit", clear)
+  proc.on("error", clear)
+  if (signal.aborted) abort()
+  return clear
+}