Designer SelectedIndex shows stale values after clamping

In the Desktop designer, a RadioButtonGroup's SelectedIndex can continue to show an invalid value after the designer has selected a different row. With three rows, entering 999 selects the last row, index 2, but the inspector still displays 999 until the control is deselected and selected again.

The same inconsistency affects PopupMenu and ComboBox, including editing multiple selected controls. The inspector should immediately reflect the accepted selection, with a mixed-value indication when the selected controls have different effective indexes. The existing -1 no-selection state must remain available.