feat: 画布聊天支持智能自动模式

1. 添加「智能自动」模型选项（默认选中）
2. 使用 qwen3-vl 先对话理解需求、优化提示词
3. 然后自动调用最佳生图模型生成图片
4. 支持历史图片上下文自动关联

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

components/canvas/CanvasChatPanel.tsx

@@ -167,12 +167,24 @@ export function CanvasChatPanel({ chatId, initialMessages = [], onClose, onOpenF
   // 过滤支持图片生成的模型
   const imageModels = modelsData?.models?.filter(m => m.supportsImageGen) || [];
   
-  // 默认选择第一个图片模型
+  // 智能自动模型选项
+  const SMART_AUTO_MODEL = {
+    id: "auto",
+    modelId: "auto",
+    displayName: "智能自动",
+    providerType: "auto",
+    supportsImageGen: true,
+  };
+  
+  // 所有可选模型（智能自动 + 生图模型）
+  const allModels = [SMART_AUTO_MODEL, ...imageModels];
+  
+  // 默认选择智能自动模型
   useEffect(() => {
-    if (imageModels.length > 0 && !selectedModelId) {
-      setSelectedModelId(imageModels[0].id);
+    if (!selectedModelId) {
+      setSelectedModelId("auto"); // 默认使用智能自动模式
     }
-  }, [imageModels, selectedModelId]);
+  }, [selectedModelId]);
   
   const currentModelIdRef = useRef(selectedModelId);
   const imageParamsRef = useRef(imageParams);
@@ -759,15 +771,37 @@ export function CanvasChatPanel({ chatId, initialMessages = [], onClose, onOpenF
                 <Paperclip className="h-4 w-4" />
               </Button>
               
-              {/* Agent Selector (Model) */}
+              {/* Agent Selector (Model) - 包含智能自动选项 */}
               <Select value={selectedModelId} onValueChange={setSelectedModelId}>
-                <SelectTrigger className="h-8 text-xs bg-blue-50 text-blue-600 border-blue-100 hover:bg-blue-100 hover:border-blue-200 transition-colors rounded-full px-3 gap-1 w-auto">
-                  <Sparkles className="h-3 w-3" />
+                <SelectTrigger className={cn(
+                  "h-8 text-xs transition-colors rounded-full px-3 gap-1 w-auto",
+                  selectedModelId === "auto" 
+                    ? "bg-gradient-to-r from-purple-50 to-blue-50 text-purple-600 border-purple-100 hover:from-purple-100 hover:to-blue-100"
+                    : "bg-blue-50 text-blue-600 border-blue-100 hover:bg-blue-100 hover:border-blue-200"
+                )}>
+                  {selectedModelId === "auto" ? (
+                    <Zap className="h-3 w-3" />
+                  ) : (
+                    <Sparkles className="h-3 w-3" />
+                  )}
                   <span className="truncate max-w-[80px]">
-                    {imageModels.find(m => m.id === selectedModelId)?.displayName || "Agent"}
+                    {allModels.find(m => m.id === selectedModelId)?.displayName || "智能自动"}
                   </span>
                 </SelectTrigger>
                 <SelectContent>
+                  {/* 智能自动选项 */}
+                  <SelectItem value="auto" className="text-xs">
+                    <div className="flex items-center gap-2">
+                      <Zap className="h-3 w-3 text-purple-500" />
+                      <span>智能自动</span>
+                      <span className="text-[10px] text-muted-foreground">先对话再生图</span>
+                    </div>
+                  </SelectItem>
+                  {/* 分隔线 */}
+                  {imageModels.length > 0 && (
+                    <div className="my-1 border-t border-border" />
+                  )}
+                  {/* 生图模型列表 */}
                   {imageModels.map(model => (
                     <SelectItem key={model.id} value={model.id} className="text-xs">
                       <div className="flex items-center gap-2">
@@ -781,13 +815,13 @@ export function CanvasChatPanel({ chatId, initialMessages = [], onClose, onOpenF
             </div>
 
             <div className="flex items-center gap-2">
-              {/* Image Params Bar */}
+              {/* Image Params Bar - 智能自动模式时也显示，用于设置最终生图参数 */}
               <ImageParamsBar
-                modelName={imageModels.find(m => m.id === selectedModelId)?.displayName}
+                modelName={allModels.find(m => m.id === selectedModelId)?.displayName}
                 initialParams={imageParams}
                 onParamsChange={handleImageParamsChange}
                 inline={true}
-                providerType={imageModels.find(m => m.id === selectedModelId)?.providerType}
+                providerType={allModels.find(m => m.id === selectedModelId)?.providerType}
               />
 
               <Button