appSurface 用例：失败只经终态事件收口，界面不再停在"还在处理"

- 新增「closes the turn from the host failure payload instead of leaving it running」：宿主发过 turn.started 之后以 failure 载荷收场并让命令失败，断言失败文案来自事件载荷（经同一份可见文案映射）、"陶泥儿正在处理"消失、终止钮消失、输入盒回到「发送」
- 同一条用例反向断言命令返回的错误原文不进聊天：那条通道只负责运行错误横幅
- 变异校验：让 reducer 不落失败说明条目时该用例变红（1 failed），恢复后绿

apps/ai-game-creator-shell/tests/appSurface/chat-composer.suite.ts

@@ -503,6 +503,62 @@ export function registerChatComposerControlTests() {
     });
   });
 
+  it('closes the turn from the host failure payload instead of leaving it running', async () => {
+    let harness: ReturnType<typeof createProjectChatRuntimeHarness> | null =
+      null;
+    const { surface } = await openDirectCodexSurface(
+      {
+        chat_with_game_creator_direct_codex: (
+          args: Record<string, unknown> | undefined,
+        ) => {
+          // 宿主先认领了这一轮（turn.started），随后失败收场：失败原因由终态事件自己带出来，
+          // 命令也以失败返回（真实宿主是先 append 终态、再把错误抛回前端）。
+          const userItemId = `direct-codex:${String(args?.clientTurnId ?? '')}:user`;
+          harness?.emitDirectThreadEvents(
+            { type: 'turn.started', at: 5_000, userItemId },
+            {
+              type: 'turn.completed',
+              status: 'failed',
+              failure: {
+                kind: 'request-rejected',
+                message: 'codex-app-server-error:context-window-exceeded',
+              },
+              at: 6_000,
+              userItemId,
+            },
+          );
+          throw new Error('模拟宿主失败：错误只走终态事件，命令只回报失败');
+        },
+      },
+      (directHarness) => {
+        harness = directHarness;
+      },
+    );
+    const composer = within(surface).getByLabelText('陶泥儿对话内容');
+    await submitDirectTurn(surface, composer, '超限的那条');
+
+    // 聊天里的失败说明来自事件载荷（经同一份可见文案映射），不是命令返回的错误文本。
+    await waitFor(() => {
+      expect(
+        within(surface).getAllByText(
+          '陶泥儿智能创作 模型上下文已超限，请缩小任务范围后重试',
+        ).length,
+      ).toBeGreaterThan(0);
+    });
+    // 终态已经到了：卡片和输入区都不能再声称"还在处理"。
+    expect(within(surface).queryAllByText('陶泥儿正在处理')).toHaveLength(0);
+    expect(within(surface).queryByRole('button', { name: '终止' })).toBeNull();
+    expect(
+      within(surface).getByRole('button', { name: '发送' }),
+    ).not.toBeNull();
+    // 命令返回那条通道只负责横幅：它不写第二条聊天文案。
+    expect(
+      within(surface).queryAllByText(
+        '模拟宿主失败：错误只走终态事件，命令只回报失败',
+      ),
+    ).toHaveLength(0);
+  });
+
   it('keeps the next queued turn busy when the write gate refuses the running one', async () => {
     const pending: Array<{ resolve: (value: string) => void }> = [];
     const deferredPolicies: Array<(value: unknown) => void> = [];