closeTab checked `tabId === this.activeTabId` AFTER awaiting page.close(),
but the page 'close' event handler can fire during that await and reassign
activeTabId — losing the race meant the last-tab auto-create never ran,
leaving the manager with zero tabs. Capture wasActive before closing, and
only reassign activeTabId when it no longer points at a live tab.
Part of the test-integrity repairs unmasked by the suite-truncation fix.
Contributed by @time-attack (PR #2230, browser-manager hunk).
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>