Follow-up to #6097. The update banner appeared 8s after load and auto-hid after
about 10s. Show it about 1s after a newer prebuilt is detected and keep it up
until the user dismisses it (click outside or the X) or runs the update; it
stays during an in-progress update so the progress is visible.
Co-authored-by: danielhanchen <michaelhan2050@gmail.com>