feat(ui): Checkbox/Radio 原子件 + 3 处原生控件采用（P2-5）

- checkboxClass/radioClass（accent-cinnabar + 统一焦点环）+ 同名测试
- Checkbox/Radio 原子件：无 label 只渲染受控原生 input 便于就地替换
- 采用：ChainStarter 链类型单选、GeneratorRunner 入库勾选、CharacterCardItem 角色勾选

apps/web/components/toolbox/GeneratorRunner.tsx

@@ -7,6 +7,7 @@ import { useToast } from "@/components/Toast";
 import { ConflictAdjudication } from "@/components/generation/ConflictAdjudication";
 import { Button } from "@/components/ui/Button";
 import { Badge } from "@/components/ui/Badge";
+import { Checkbox } from "@/components/ui/Checkbox";
 import { Field } from "@/components/ui/Field";
 import { StatusNote } from "@/components/ui/StatusNote";
 import { TextArea } from "@/components/ui/TextArea";
@@ -380,8 +381,7 @@ function PreviewRow({
   return (
     <li className="flex gap-2 rounded border border-line bg-bg p-3 text-sm">
       {selectable ? (
-        <input
-          type="checkbox"
+        <Checkbox
           checked={checked}
           onChange={() => onToggle(index)}
           className="mt-1"