收口前端平台组件库能力

新增 PlatformUiKit 通用弹窗、按钮、状态、空态、媒体、表单和标签等公共组件
迁移结果页、创作工作台、认证入口、RPG 暗色面板和运行态弹窗的重复 UI chrome
补充组件测试、页面回归测试、技术文档和 Hermes 共享决策记录

src/components/common/LegalDocumentModal.tsx

@@ -5,6 +5,7 @@ import type {
   LegalDocument,
   LegalDocumentBlock,
 } from './legalDocuments';
+import { PlatformActionButton } from './PlatformActionButton';
 import { UnifiedModal } from './UnifiedModal';
 
 type LegalDocumentModalProps = {
@@ -95,13 +96,14 @@ export function LegalDocumentModal({
       bodyClassName="px-4 py-0 sm:px-5"
       footerClassName="justify-stretch sm:justify-end"
       footer={
-        <button
-          type="button"
+        <PlatformActionButton
           onClick={onClose}
-          className="platform-button platform-button--secondary min-h-0 w-full rounded-[0.9rem] px-4 py-2.5 text-sm sm:w-auto"
+          tone="secondary"
+          fullWidth
+          className="min-h-0 rounded-[0.9rem] sm:w-auto"
         >
           我知道了
-        </button>
+        </PlatformActionButton>
       }
     >
       <div className="max-h-[min(64vh,34rem)] overflow-y-auto py-4 pr-1">