feat: 画布聊天面板功能增强

1. 加载历史对话消息（从 API 获取）
2. 选中画布图片时自动添加到对话附件
3. 修复类型错误

Co-authored-by: Cursor <cursoragent@cursor.com>

components/canvas/CanvasChatPanel.tsx

@@ -104,6 +104,46 @@ export function CanvasChatPanel({ chatId, initialMessages = [], onClose, onOpenF
   // Canvas store
   const addNode = useCanvasStore((state) => state.addNode);
   const nodes = useCanvasStore((state) => state.nodes);
+  const selectedNodeIds = useCanvasStore((state) => state.selectedNodeIds);
+  
+  // 获取纯 UUID（去掉 canvas- 前缀）用于 API 调用
+  const rawChatId = chatId.startsWith('canvas-') 
+    ? chatId.replace('canvas-', '') 
+    : chatId;
+  
+  // 从 API 加载历史消息
+  const { data: historyData, isLoading: isLoadingHistory } = useSWR<{
+    messages: ChatMessage[];
+  }>(rawChatId ? `/api/messages?chatId=${rawChatId}` : null, fetcher);
+  
+  // 获取选中的图片节点
+  const selectedImageNodes = nodes.filter(
+    n => selectedNodeIds.includes(n.id) && n.type === 'image' && (n.data as any)?.src
+  );
+  
+  // 当选中画布中的图片时，自动添加到附件
+  useEffect(() => {
+    if (selectedImageNodes.length > 0) {
+      const newAttachments: Attachment[] = selectedImageNodes.map(node => {
+        const data = node.data as any;
+        return {
+          url: data.src,
+          name: data.prompt || '画布图片',
+          contentType: 'image/jpeg',
+        };
+      });
+      
+      // 只添加还没在附件中的图片
+      setAttachments(prev => {
+        const existingUrls = new Set(prev.map(a => a.url));
+        const toAdd = newAttachments.filter(a => !existingUrls.has(a.url));
+        if (toAdd.length > 0) {
+          return [...prev, ...toAdd];
+        }
+        return prev;
+      });
+    }
+  }, [selectedImageNodes.length, selectedNodeIds]);
   
   // 获取模型列表
   const { data: modelsData } = useSWR<{
@@ -145,6 +185,11 @@ export function CanvasChatPanel({ chatId, initialMessages = [], onClose, onOpenF
     imageParamsRef.current = imageParams;
   }, [imageParams]);
 
+  // 合并 initialMessages 和历史消息
+  const mergedInitialMessages = historyData?.messages?.length 
+    ? historyData.messages 
+    : initialMessages;
+  
   const {
     messages,
     setMessages,
@@ -153,7 +198,7 @@ export function CanvasChatPanel({ chatId, initialMessages = [], onClose, onOpenF
     stop,
   } = useChat<ChatMessage>({
     id: chatId,
-    messages: initialMessages,
+    messages: mergedInitialMessages,
     experimental_throttle: 100,
     generateId: generateUUID,
     transport: new DefaultChatTransport({
@@ -217,6 +262,16 @@ export function CanvasChatPanel({ chatId, initialMessages = [], onClose, onOpenF
       toast.error(error.message || "生成失败");
     },
   });
+  
+  // 当历史消息加载完成后，更新消息列表
+  const hasLoadedHistory = useRef(false);
+  useEffect(() => {
+    if (historyData?.messages?.length && !hasLoadedHistory.current) {
+      hasLoadedHistory.current = true;
+      setMessages(historyData.messages);
+      console.log('[CanvasChat] 已加载历史消息:', historyData.messages.length);
+    }
+  }, [historyData, setMessages]);
 
   // 监听消息变化，提取图片并添加到画布
   const processedMessageIds = useRef<Set<string>>(new Set());
@@ -574,9 +629,9 @@ export function CanvasChatPanel({ chatId, initialMessages = [], onClose, onOpenF
                   )}
                 >
                   {/* 附件预览 */}
-                  {message.attachments && message.attachments.length > 0 && (
+                  {(message as any).attachments && (message as any).attachments.length > 0 && (
                     <div className="flex flex-wrap gap-2 mb-2">
-                      {message.attachments.map((att: any, i: number) => (
+                      {(message as any).attachments.map((att: any, i: number) => (
                         <img
                           key={i}
                           src={att.url}