contentPadding

Padding="10,3,10,5" at 0.75, as the current theme has scaled it.

Composable rather than a constant, and that is the whole point: it is read out of KvadrantMetrics so a caller that scales the metric set scales this with it. As a constant it was the one measurement on a button that did not move, and a scaled-up button came out with a grown line of text inside an ungrown frame.