fix(desktop): DeerFlow UI — ChatArea refactor + ai-elements + dead CSS cleanup

ChatArea retry button uses setInput instead of direct sendToGateway,
fix bootstrap spinner stuck for non-logged-in users,
remove dead CSS (aurora-title/sidebar-open/quick-action-chips),
add ai components (ReasoningBlock/StreamingText/ChatMode/ModelSelector/TaskProgress),
add ClassroomPlayer + ResizableChatLayout + artifact panel

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

desktop/src/components/ClassroomPreviewer.tsx

@@ -67,6 +67,7 @@ interface ClassroomPreviewerProps {
   data: ClassroomData;
   onClose?: () => void;
   onExport?: (format: 'pptx' | 'html' | 'pdf') => void;
+  onOpenFullPlayer?: () => void;
 }
 
 // === Sub-Components ===
@@ -271,6 +272,7 @@ function OutlinePanel({
 export function ClassroomPreviewer({
   data,
   onExport,
+  onOpenFullPlayer,
 }: ClassroomPreviewerProps) {
   const [currentSceneIndex, setCurrentSceneIndex] = useState(0);
   const [isPlaying, setIsPlaying] = useState(false);
@@ -398,6 +400,15 @@ export function ClassroomPreviewer({
           </p>
         </div>
         <div className="flex items-center gap-2">
+          {onOpenFullPlayer && (
+            <button
+              onClick={onOpenFullPlayer}
+              className="flex items-center gap-1.5 px-3 py-1.5 text-sm bg-indigo-100 dark:bg-indigo-900/30 text-indigo-700 dark:text-indigo-300 rounded-md hover:bg-indigo-200 dark:hover:bg-indigo-900/50 transition-colors"
+            >
+              <Play className="w-4 h-4" />
+              完整播放器
+            </button>
+          )}
           <button
             onClick={() => handleExport('pptx')}
             className="flex items-center gap-1.5 px-3 py-1.5 text-sm bg-orange-100 dark:bg-orange-900/30 text-orange-700 dark:text-orange-300 rounded-md hover:bg-orange-200 dark:hover:bg-orange-900/50 transition-colors"