XWIKI-24807: AdministrationSectionPage#clickSave() doesn't wait for the page reload, causing flickering StaleElementReferenceException in administration UI tests

* clickSave(boolean) now synchronizes on the full-page reload triggered by a
  non-async section's save button, using the existing
  addPageNotYetReloadedMarker()/waitUntilPageIsReloaded() idiom, instead of
  returning immediately after the click
* this avoids a race where a caller reading back the saved value right after
  clickSave() can hit a stale element from the page being unloaded

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

Author: surli

xwiki-platform-core/xwiki-platform-administration/xwiki-platform-administration-test/xwiki-platform-administration-test-pageobjects/src/main/java/org/xwiki/administration/test/po/AdministrationSectionPage.java

@@ -145,12 +145,18 @@ public void clickSave(boolean wait)
             saveButton = getDriver().findElement(By.xpath("//input[@type='submit'][@name='action_saveandcontinue']"));
         } else {
             saveButton = getDriver().findElement(By.xpath("//input[@type='submit'][@name='formactionsac']"));
+            // The button triggers a full page reload. Mark the current page so that we can be sure the reload has
+            // actually happened before continuing, otherwise the caller can race the navigation and interact with
+            // an element from the page being unloaded, causing a StaleElementReferenceException.
+            getDriver().addPageNotYetReloadedMarker();
         }
         saveButton.click();
 
         if (wait) {
             // Wait until the page is really saved.
             waitForNotificationSuccessMessage("Saved");
+        } else if (!this.asyncSave) {
+            getDriver().waitUntilPageIsReloaded();
         }
     }