优化 AI 设计任务失败提示

问题：客户端直接展示 policy_blocked 等内部错误码。

实现：统一转换为中文设计语言提示，并补充策略拦截场景回归测试。

src/pages/ImageCanvas/index.tsx

@@ -37,6 +37,19 @@ import type {
 } from '../../../shared/image-workspace';
 
 const ACTIVE_TASK_STATUSES = new Set<DesignTaskStatus>(['queued', 'running']);
+const TASK_FAILURE_MESSAGES: Record<string, string> = {
+  policy_blocked: '内容可能涉及版权或安全风险，请调整设计后重试',
+  budget_denied: '当前设计点不足，无法开始生成',
+  quote_expired: '生成方案已过期，请重新确认',
+  asset_rejected: '生成结果未通过媒体检查，请调整设计后重试',
+  dependency_unavailable: '生成服务暂时不可用，请稍后重试',
+  submission_unknown: '正在确认生成请求状态，请稍后查看',
+  submission_not_accepted: '生成请求未被服务接受，请重新确认后再试',
+  generation_failed: '生成未完成，请调整设计或稍后重试',
+  result_persist_failed: '生成结果保存失败，请稍后重试',
+  cancelled: '生成任务已取消',
+  expired: '生成任务已过期，请重新确认',
+};
 const CONFIRMATION_UNAVAILABLE_MESSAGE = (
   '当前没有可确认的生成报价，请先让设计 Agent 完成方案与报价。'
 );
@@ -61,6 +74,10 @@ function taskStatusLabel(status: DesignTaskStatus): string {
   return '失败';
 }
 
+function taskFailureMessage(code: string): string {
+  return TASK_FAILURE_MESSAGES[code] ?? '生成未完成，请稍后重试';
+}
+
 function mediumLabel(medium: 'image' | 'video'): string {
   return medium === 'video' ? '视频' : '图片';
 }
@@ -153,7 +170,7 @@ function TaskCard({ task }: { task: DesignGenerationTask }) {
         </p>
         {task.failureCode ? (
           <p role="alert" className="mt-2 rounded-lg bg-destructive/10 px-2 py-1.5 text-[11px] font-semibold text-destructive">
-            {task.failureCode}
+            {taskFailureMessage(task.failureCode)}
           </p>
         ) : null}
       </div>

tests/unit/image-canvas-page.test.tsx

@@ -482,6 +482,21 @@ describe('ImageCanvas Workspace-first design experience', () => {
     expect(confirmImageWorkspaceGenerationMock).not.toHaveBeenCalled();
   });
 
+  it('renders policy-blocked generation tasks with a user-facing design message', async () => {
+    fetchImageWorkspaceTasksMock.mockResolvedValue([{
+      ...taskFixture,
+      status: 'failed',
+      failureCode: 'policy_blocked',
+      resultAssets: [],
+    }]);
+
+    render(<MemoryRouter><ImageCanvas /></MemoryRouter>);
+
+    const alert = await screen.findByRole('alert');
+    expect(alert).toHaveTextContent('内容可能涉及版权或安全风险，请调整设计后重试');
+    expect(alert).not.toHaveTextContent('policy_blocked');
+  });
+
   it('renders a new task pushed by the design event stream without repeated polling', async () => {
     const queuedTask = {
       ...taskFixture,