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/PlatformQuantityBadge.test.tsx

@@ -0,0 +1,31 @@
+/* @vitest-environment jsdom */
+
+import { render, screen } from '@testing-library/react';
+import { expect, test } from 'vitest';
+
+import { PlatformQuantityBadge } from './PlatformQuantityBadge';
+
+test('renders a dark bottom-right quantity badge by default', () => {
+  render(<PlatformQuantityBadge>3</PlatformQuantityBadge>);
+
+  const badge = screen.getByText('3');
+
+  expect(badge.className).toContain('absolute');
+  expect(badge.className).toContain('bottom-1');
+  expect(badge.className).toContain('right-1');
+  expect(badge.className).toContain('bg-black/70');
+  expect(badge.className).toContain('text-[10px]');
+});
+
+test('supports custom class names', () => {
+  render(
+    <PlatformQuantityBadge className="custom-quantity">
+      12
+    </PlatformQuantityBadge>,
+  );
+
+  const badge = screen.getByText('12');
+
+  expect(badge.className).toContain('rounded-full');
+  expect(badge.className).toContain('custom-quantity');
+});