fix: 网页端Anthropic Claude对话格式去除system角色，改为assistant角色

Yi.Ai.Vue3/src/utils/apiFormatConverter.ts

@@ -184,7 +184,7 @@ export function toClaudeFormat(messages: UnifiedMessage[]): { messages: ClaudeMe
     });
   }
 
-  return { messages: claudeMessages, system: systemPrompt };
+  return { messages: claudeMessages };
 }
 
 /**
@@ -521,16 +521,16 @@ export function convertToApiFormat(
       };
     }
     case ApiFormatType.Messages: {
-      const { messages: claudeMessages, system } = toClaudeFormat(messages);
+      const { messages: claudeMessages } = toClaudeFormat(messages);
       const request: any = {
         model,
         messages: claudeMessages,
         max_tokens: 32000,
         stream,
       };
-      if (system) {
-        request.system = system;
-      }
+      // if (system) {
+      //   request.system = system;
+      // }
       return request;
     }
     case ApiFormatType.GenerateContent: {