test: add mutex to clipboard copy & paste operation to reduce flaky (#11884)

tests/kit/src/utils/page-logic.ts

@@ -60,8 +60,7 @@ export async function type(page: Page, content: string, delay = 50) {
 }
 
 export const createLinkedPage = async (page: Page, pageName?: string) => {
-  // fixme: workaround for @ popover not showing up when editor is not ready
-  await page.waitForTimeout(500);
+  await waitForEditorLoad(page);
   await page.keyboard.type('@', { delay: 50 });
   const linkedPagePopover = page.locator('.linked-doc-popover');
   await expect(linkedPagePopover).toBeVisible();