feat(learning): make practice scoring authoritative

Tiku.Infrastructure/PlatformAdmin/PlatformQuestionBankService.cs

@@ -4,6 +4,7 @@ using System.Text.Json;
 using Microsoft.EntityFrameworkCore;
 using Microsoft.Extensions.DependencyInjection;
 using Tiku.Application.Assets;
+using Tiku.Application.Learning;
 using Tiku.Application.PlatformAdmin;
 using Tiku.Application.Security;
 using Tiku.Domain.Common;
@@ -620,6 +621,15 @@ internal sealed class PlatformQuestionBankService(
         var type = string.IsNullOrWhiteSpace(command.Type) ? "choice" : command.Type.Trim();
         if (!SupportedQuestionTypes.Contains(type)) throw Error("题型不受支持。", "question_type_invalid");
         if (command.Difficulty is < 1 or > 5) throw Error("难度必须在 1 到 5 之间。", "question_difficulty_invalid");
+        if (ParseQuestionStatus(command.Status) == QuestionStatus.Published &&
+            !QuestionGrader.HasValidAuthoritativeAnswer(
+                type,
+                command.CorrectOptionIndex,
+                command.CorrectOptionIndices,
+                command.AnswerText))
+        {
+            throw Error("发布题目必须提供有效的标准答案。", "question_grading_rule_invalid");
+        }
     }
 
     private static void ApplyQuestion(Question question, UpsertPlatformQuestionCommand command, Guid entryId, Guid nodeId)