RealtimeWYSIWYGEditorIT#restrictScriptMacroExecution is flickering

New failure on 2026-09-30, stable-18.4.x #217 (commit 89eec5c383f, default configuration: Jetty standalone, HSQLDB, Firefox). This time it is not a timeout but an assertion:

org.opentest4j.AssertionFailedError: expected: <true> but was: <false>
	at org.xwiki.realtime.wysiwyg.test.ui.RealtimeWYSIWYGEditorIT.restrictScriptMacroExecution(RealtimeWYSIWYGEditorIT.java:1294)

This is assertTrue(text.contains("before\nFailed to execute the [velocity] macro.")) on the second tab, right after secondTextArea.waitForContentRefresh(firstRefreshCounter), once the first user has inserted the injected Velocity macro. The assertFalse(text.contains("injected")) that follows was never reached, and the assertion has no message, so the CI report does not show the content. It cannot tell a content read before the last re-render (test race) from the macro having been executed (script right not enforced).

• Local verification on the same commit: the whole realtime-wysiwyg module passed with the CI Maven options, and the test passed 20/20 when repeated alone on Firefox.
• CI history: 1 failure in the last 20 builds of the stable-18.4.x main job; passes on master, stable-18.8.x and stable-17.10.x.

So this still looks like a flicker. The failing assertions should print the text they check (as the assertFalse ones already do), so that the next failure can be classified.