feat(ui): 实现消息 parts 有序渲染

- Server: API 返回 parts 数组保持原始顺序
- Server: 添加 MessagePart 类型定义 (text/tool/reasoning)
- UI: ChatMessage 按 parts 顺序交叉渲染文本和工具调用
- UI: 新增 ToolPartItem 组件渲染单个工具 part
- UI: useChat 创建消息时添加 parts 字段

packages/ui/src/hooks/useChat.ts

@@ -123,11 +123,13 @@ export function useChat({ sessionId, onError, onSessionNotFound, onSessionUpdate
 
           case 'done':
             setState((prev) => {
+              const content = message.payload?.content || prev.streamingContent;
               const newMessage: Message = {
                 id: message.payload?.id || `assistant-${Date.now()}-${Math.random().toString(36).slice(2, 9)}`,
                 role: 'assistant',
-                content: message.payload?.content || prev.streamingContent,
                 timestamp: message.payload?.timestamp || new Date().toISOString(),
+                parts: [{ type: 'text', id: `text-${Date.now()}`, text: content }],
+                content,
               };
               return {
                 ...prev,
@@ -141,11 +143,13 @@ export function useChat({ sessionId, onError, onSessionNotFound, onSessionUpdate
           case 'message_received':
             // 用户消息已确认 - 构建完整的消息对象
             setState((prev) => {
+              const content = message.payload?.content || '';
               const userMessage: Message = {
                 id: `user-${Date.now()}-${Math.random().toString(36).slice(2, 9)}`,
                 role: 'user',
-                content: message.payload?.content || '',
                 timestamp: new Date().toISOString(),
+                parts: [{ type: 'text', id: `text-${Date.now()}`, text: content }],
+                content,
               };
               return {
                 ...prev,