统一创建：8s不扩展剧本

components/pages/create-video/CreateInput/ConfigPanel.tsx

@@ -100,7 +100,14 @@ export const ConfigPanel = ({
             <Dropdown 
                 menu={{ 
                     items: durationMenuItems,
-                    onClick: ({ key }) => onConfigChange('videoDuration', key as VideoDurationValue),
+                    onClick: ({ key }) => {
+                        onConfigChange('videoDuration', key as VideoDurationValue);
+                        if (key === '8s') {
+                            onConfigChange('expansion_mode', false);
+                        } else {
+                            onConfigChange('expansion_mode', true);
+                        }
+                    },
                     className: 'bg-[#1a1a1a] border border-white/10'
                 }} 
                 trigger={['click']}