Fix attachment preview test act helpers

ui/src/pages/IssueDetail.test.tsx

@@ -2,7 +2,8 @@
 
 import { QueryClient, QueryClientProvider } from "@tanstack/react-query";
 import type { Agent, Issue, IssueTreeControlPreview, IssueTreeHold } from "@paperclipai/shared";
-import { act, type AnchorHTMLAttributes, type ButtonHTMLAttributes, type ReactNode } from "react";
+import type { AnchorHTMLAttributes, ButtonHTMLAttributes, ReactNode } from "react";
+import { flushSync } from "react-dom";
 import { createRoot, type Root } from "react-dom/client";
 import { afterEach, beforeEach, describe, expect, it, vi } from "vitest";
 import { canBoardResolveRecoveryAction, IssueDetail } from "./IssueDetail";
@@ -357,6 +358,14 @@ vi.mock("@/components/ui/textarea", () => ({
 // eslint-disable-next-line @typescript-eslint/no-explicit-any
 (globalThis as any).IS_REACT_ACT_ENVIRONMENT = true;
 
+async function act(callback: () => void | Promise<void>) {
+  let result: void | Promise<void> = undefined;
+  flushSync(() => {
+    result = callback();
+  });
+  await result;
+}
+
 function createDeferred<T>() {
   let resolve!: (value: T) => void;
   const promise = new Promise<T>((innerResolve) => {