Running a large test suite can make Studio unresponsive

Running a project with a large test suite can make Objo Studio stop responding while the tests continue to execute in the isolated Test Host. On macOS this presents as a spinning beachball: test progress, the Stop button, window controls, and the rest of Studio become unusable until the UI catches up or the application is force-quit.

Test execution must never monopolise Studio's UI thread. Studio should remain fully responsive throughout discovery, execution, progress reporting, cancellation, and final result presentation, regardless of how many tests complete in quick succession.