disposeBrowserHandle awaited Puppeteer's browser.close() for the headless
kind with no timeout. browser.close() resolves only once Chromium fully
exits, so a wedged process (a Windows failure mode) left releaseTab stuck
in the "Closing tab" phase forever.
Cap the close at 5s and force-kill the Chromium process tree on timeout so
the tool call always releases.
Fixes#5260
