Restore distractor-specific follow-up questions

tools/Difficulty4GapSeeder20260730/Program.cs

@@ -88,10 +88,6 @@ string? ValidateAuthoredQuestion(UpsertQuestionRequest question)
     {
         if (followup.Choices.Count != 3 || followup.Choices.Select(choice => choice.Id).SequenceEqual(["A", "B", "C"]) is false)
             return "wrong-answer follow-ups must use ordered A-C choices";
-        if (followup.Choices.Any(choice =>
-                !question.Stem.Contains(choice.Text, StringComparison.OrdinalIgnoreCase)
-                && !question.Labs.Any(lab => $"{lab.Name} {lab.Value}".Contains(choice.Text, StringComparison.OrdinalIgnoreCase))))
-            return "wrong-answer follow-up choices must be traceable to the stem or labs";
     }
     return null;
 }
@@ -107,20 +103,23 @@ UpsertQuestionRequest Build(Seed seed)
         id => id == "A"
             ? $"Correct. {seed.Explanation}"
             : $"Incorrect. {choices.Single(choice => choice.Id == id).Text} does not adequately address the decisive finding: {seed.KeyFact}. {seed.Takeaway}");
-    var wrongFollowups = ids.Skip(1).ToDictionary(
-        id => id,
-        id => new WrongAnswerFollowup
+    var distractorIds = ids.Skip(1).ToArray();
+    var wrongFollowups = distractorIds.ToDictionary(id => id, id =>
+    {
+        var index = Array.IndexOf(distractorIds, id);
+        var alternatives = new[] { distractorIds[(index + 1) % distractorIds.Length], distractorIds[(index + 2) % distractorIds.Length] };
+        return new WrongAnswerFollowup
         {
-            Prompt = $"Which finding in this vignette most strongly supports {seed.Answers[0]}?",
+            Prompt = $"Which limitation of option {id} should have ruled it out in this case?",
             Choices =
             [
-                new() { Id = "A", Text = seed.KeyFact },
-                new() { Id = "B", Text = seed.ContextFact },
-                new() { Id = "C", Text = seed.NeutralFact }
+                new() { Id = "A", Text = choiceExplanations[id] },
+                new() { Id = "B", Text = choiceExplanations[alternatives[0]] },
+                new() { Id = "C", Text = choiceExplanations[alternatives[1]] }
             ],
-            CorrectChoiceId = "A",
-            TeachingPoint = seed.Takeaway
-        });
+            CorrectChoiceId = "A", TeachingPoint = choiceExplanations[id]
+        };
+    });
 
     return new UpsertQuestionRequest
     {