Refactor: CheckboxGroup and RadioGroup return ChoiceResult

They returned InputResult with an Input nobody read (nil for RadioGroup).

docs/components/029-checkbox.md

@@ -17,7 +17,7 @@ mujica.CheckboxGroup(c, "Notifications", []mujica.CheckboxItem{
 
 ```go
 func Checkbox(c *ui.Context, value *bool, label string, opts CheckboxOptions) *ui.Element
-func CheckboxGroup(c *ui.Context, label string, items []CheckboxItem, opts CheckboxGroupOptions) InputResult
+func CheckboxGroup(c *ui.Context, label string, items []CheckboxItem, opts CheckboxGroupOptions) ChoiceResult
 ```
 
 ## 参数

docs/components/030-radio-group.md

@@ -13,7 +13,7 @@ if mujica.RadioGroup(c, &size, items, mujica.RadioGroupOptions{Label: "Size"}).C
 }
 ```
 
-签名：`func RadioGroup[T comparable](c *ui.Context, value *T, items []RadioItem[T], opts RadioGroupOptions) InputResult`
+签名：`func RadioGroup[T comparable](c *ui.Context, value *T, items []RadioItem[T], opts RadioGroupOptions) ChoiceResult`
 
 ## 参数