继续收口详情页头部动作组合

沉淀 PlatformDetailTopbar 与 PlatformDetailShareActions 共享骨架
接入 RPG 世界详情与公开作品详情的返回复制分享动作组合
补充测试护栏与文档决策记录

src/components/common/PlatformDetailTopbar.test.tsx

@@ -0,0 +1,49 @@
+/* @vitest-environment jsdom */
+
+import { fireEvent, render, screen } from '@testing-library/react';
+import { expect, test, vi } from 'vitest';
+
+import { PlatformDetailTopbar } from './PlatformDetailTopbar';
+
+test('renders pill back action with trailing slot', () => {
+  const onBack = vi.fn();
+
+  render(
+    <PlatformDetailTopbar
+      onBack={onBack}
+      className="grid-cols-[auto,minmax(0,1fr),auto]"
+      backButtonClassName="px-3"
+      trailing={<span>已发布</span>}
+    />,
+  );
+
+  const button = screen.getByRole('button', { name: '返回' });
+
+  expect(button.className).toContain('platform-button--ghost');
+  expect(button.className).toContain('px-3');
+  expect(screen.getByText('已发布')).toBeTruthy();
+
+  fireEvent.click(button);
+
+  expect(onBack).toHaveBeenCalledTimes(1);
+});
+
+test('renders icon back action and centered title', () => {
+  render(
+    <PlatformDetailTopbar
+      onBack={vi.fn()}
+      backVariant="icon"
+      backButtonClassName="detail-icon-back"
+      title="详情"
+      titleClassName="detail-topbar-title"
+      trailing={<span className="invisible">占位</span>}
+    />,
+  );
+
+  const button = screen.getByRole('button', { name: '返回' });
+  const title = screen.getByText('详情');
+
+  expect(button.className).toContain('platform-icon-button');
+  expect(button.className).toContain('detail-icon-back');
+  expect(title.className).toContain('detail-topbar-title');
+});