Updates radio-group styling across Base UI and Radix variants (examples, registries, and theme CSS/JSON) to use checked-state background/foreground classes and a simple span indicator instead of the CircleIcon/IconPlaceholder, aligning focus/invalid ring behavior across styles. This changes the look and reduces icon dependencies, so consumers may see a visual diff (especially checked/invalid states) and should verify accessibility/contrast and that data-checked/aria-invalid selectors behave consistently in all themes and RTL layouts.