chore: import upstream snapshot with attribution

open-sse/utils/setupPolyfill.ts

@@ -0,0 +1,33 @@
+// Polyfill worker_threads.markAsUncloneable for Node.js < 21 compatibility (specifically Node 20.20.2)
+import worker_threads from "node:worker_threads";
+import { WebSocket } from "ws";
+
+if (worker_threads && !worker_threads.markAsUncloneable) {
+  (worker_threads as any).markAsUncloneable = function (obj: any) {
+    if (worker_threads.markAsUntransferable) {
+      try {
+        worker_threads.markAsUntransferable(obj);
+      } catch {
+        // no-op
+      }
+    }
+  };
+}
+
+// Polyfill Promise.withResolvers for Node.js < 22 compatibility (specifically Node 20.20.2)
+if (typeof Promise.withResolvers === "undefined") {
+  Promise.withResolvers = function <T>() {
+    let resolve!: (value: T | PromiseLike<T>) => void;
+    let reject!: (reason?: any) => void;
+    const promise = new Promise<T>((res, rej) => {
+      resolve = res;
+      reject = rej;
+    });
+    return { promise, resolve, reject };
+  } as any;
+}
+
+// Polyfill WebSocket for Node.js < 22 compatibility (specifically Node 20.20.2)
+if (typeof globalThis.WebSocket === "undefined") {
+  (globalThis as any).WebSocket = WebSocket;
+}