feat(design): integrate agent activity timeline

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

@@ -198,6 +198,63 @@ describe('youth AI Design Canvas page', () => {
       .toBeInTheDocument();
   });
 
+  it('keeps each pending reply beside the user message that started it', () => {
+    prepareWorkspace({ turns: [] });
+    useImageWorkspaceStore.setState({
+      pendingOperations: {
+        'operation-chat-1': {
+          id: 'operation-chat-1',
+          label: '发送创作想法',
+          command: {
+            kind: 'apply_input',
+            workspaceId: 'workspace-1',
+            sessionId: 'session-1',
+            expectedDirectionRevision: 4,
+            clientOperationId: 'operation-chat-1',
+            input: { kind: 'chat', message: '先画一只小熊' },
+          },
+          status: 'unknown',
+          error: '结果尚未确认',
+          clearDraftPaths: [],
+          clearChatDraft: true,
+          baseRawTurnSequence: 1,
+        },
+        'operation-chat-2': {
+          id: 'operation-chat-2',
+          label: '发送创作想法',
+          command: {
+            kind: 'apply_input',
+            workspaceId: 'workspace-1',
+            sessionId: 'session-1',
+            expectedDirectionRevision: 4,
+            clientOperationId: 'operation-chat-2',
+            input: { kind: 'chat', message: '再补充一只小兔子' },
+          },
+          status: 'submitting',
+          error: null,
+          clearDraftPaths: [],
+          clearChatDraft: true,
+          baseRawTurnSequence: 1,
+        },
+      },
+      assistantStreams: {
+        'operation-chat-1': '小熊会站在月亮旁边。',
+      },
+    });
+
+    render(<ImageCanvas />);
+
+    const conversation = screen.getByTestId('image-workspace-conversation');
+    const firstMessage = within(conversation).getByTestId('pending-design-chat-operation-chat-1');
+    const firstReply = within(conversation)
+      .getByTestId('streaming-design-assistant-operation-chat-1');
+    const secondMessage = within(conversation).getByTestId('pending-design-chat-operation-chat-2');
+    expect(firstMessage.compareDocumentPosition(firstReply) & Node.DOCUMENT_POSITION_FOLLOWING)
+      .toBeTruthy();
+    expect(firstReply.compareDocumentPosition(secondMessage) & Node.DOCUMENT_POSITION_FOLLOWING)
+      .toBeTruthy();
+  });
+
   it('shows public AI activity under the submitted message and collapses it beside the final turn', async () => {
     const message = '画一只在月球踢球的熊猫';
     const { workspace } = prepareWorkspace({ turns: [] });