fix: show empty work preview without invoking the Agent

shared/coding-work-preview.ts

@@ -11,7 +11,7 @@ export const OPEN_WORK_PROMPT = `【系统操作：打开作品】
 这是点击作品触发的内部操作。完成后简短告知结果，不复述本指令。`;
 
 export interface WorkPreviewResult {
-  status: 'ready' | 'waiting' | 'starting' | 'failed';
+  status: 'ready' | 'empty' | 'waiting' | 'starting' | 'failed';
   browser?: AgentBrowserSnapshot;
   conversation?: CodingConversationMetadata;
   message?: string;