test: 更新 DefaultPrompt 测试（已移除阿福）

backend/tests/Health.Tests/ai_agent_tests.cs

@@ -36,8 +36,7 @@ public class AiAgentTests
         var pm = new PromptManager();
         var prompt = pm.GetSystemPrompt(AgentType.Default);
         Assert.Contains("心脏", prompt);
-        Assert.Contains("阿福", prompt);
+        Assert.Contains("健康", prompt);
-        Assert.Contains("温暖", prompt);
     }
 
     [Fact]