Headless test browsers no longer speak out loud

Agents test pages in a headless browser, and demo videos are recorded in one too. Until now, a page that read text aloud with the browser's speech feature spoke through the computer's system voice, even though browser sound was muted. During an agent's tests that could mean a voice saying a word every half minute. Both browsers now replace the page's speech with a silent one, so nothing reaches the speakers. Pages still behave as if the text had been spoken: each sentence takes about as long as saying it would, and stopping or pausing works as usual, so pages that wait for speech to finish keep running.