Settings rows: controls do not share a right edge, and the checkbox is dwarfed by its button #59

On the repository settings page each row is label, control, button. Rows whose control stretches — a text input, a select — push the button to the right edge. Rows whose control does not — a checkbox, a number — leave the control beside its label with the button stranded next to it, so the page has no consistent right edge.

The checkbox is also the wrong weight for the row it sits in: the native control renders at 22.5px beside a 39px button, next to text inputs and selects that are 38px.