UiSlider takes v-model, min, max, step and disabled
over Core's native range input, emits numbers, and with `hold` never
rewrites a focused handle and takes the model back on blur. It is a
functional render function, so the portable style parameter rows use it
too. The Display, Radio, RTL-SDR, Cockpit, mission replay and style
parameter sliders render with it; server-rendered markup keeps their
default values.