ChatView.dom.test.ts leaks a @tanstack/virtual timer past jsdom teardown (CI flake) #406

Intermittent CI failure: all tests pass but vitest reports one unhandled error — ReferenceError: window is not defined from @tanstack/virtual-core Timeout._onTimeout firing after the jsdom environment is torn down (originates in ChatView.dom.test.ts). Cost a false-red on #401 (green on rerun). Fix: dispose/flush the virtualizer (or advance+clear fake timers) before env teardown.