fix: 修复画布聊天面板发送消息格式

1. 修复 handleSend 中 parts 数组的顺序（文件在前，文本在后）
2. 添加 videoParams: undefined 确保 schema 兼容
3. 添加调试日志帮助排查问题

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

components/canvas/CanvasChatPanel.tsx

@@ -153,13 +153,20 @@ export function CanvasChatPanel({ chatId, initialMessages = [], onClose, onOpenF
       api: "/api/chat",
       fetch: fetchWithErrorHandlers,
       prepareSendMessagesRequest(request) {
+        console.log("[CanvasChat] Preparing request:", {
+          id: request.id,
+          modelId: currentModelIdRef.current,
+          imageParams: imageParamsRef.current,
+          lastMessage: request.messages.at(-1),
+        });
         return {
           body: {
             id: request.id,
             message: request.messages.at(-1),
             selectedChatModel: currentModelIdRef.current,
             selectedVisibilityType: "private",
-            imageParams: imageParamsRef.current, // 传递图片参数
+            videoParams: undefined, // 必须传递，即使是 undefined
+            imageParams: imageParamsRef.current || undefined, // 传递图片参数
             ...request.body,
           },
         };
@@ -252,31 +259,28 @@ export function CanvasChatPanel({ chatId, initialMessages = [], onClose, onOpenF
       return;
     }
     
-    // 构建 parts 数组：文本 + 文件
+    // 构建 parts 数组：文件在前，文本在后（与 multimodal-input 一致）
     const parts: any[] = [];
     
-    // 添加文本部分
-    if (input.trim()) {
-      parts.push({ type: "text", text: input });
-    }
-    
     // 添加文件部分（作为 file 类型的 part）
     attachments.forEach(a => {
       parts.push({
-        type: "file",
+        type: "file" as const,
         mediaType: a.contentType,
         name: a.name,
         url: a.url,
       });
     });
     
-    // 如果没有文本但有附件，添加一个空的文本提示
-    if (!input.trim() && attachments.length > 0) {
-      parts.unshift({ type: "text", text: "请处理这张图片" });
+    // 添加文本部分
+    const textContent = input.trim() || (attachments.length > 0 ? "请处理这张图片" : "");
+    if (textContent) {
+      parts.push({ type: "text" as const, text: textContent });
     }
     
+    // 使用与 multimodal-input 相同的格式发送消息
     sendMessage({
-      role: "user" as const,
+      role: "user",
       parts: parts,
     });