feat(core): 追加 GeneratedQuestion frozen dataclass

跨层共享类型，被 core/evolution/ 和 app/harness/、app/question_gen/ 使用。
frozen=True + tuple 字段确保不可变。无默认值（显式传入）。

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

tests/unit/test_core_types.py

@@ -1,9 +1,10 @@
 """core/types.py 单元测试。"""
+
 from __future__ import annotations
 
 import pytest
 
-from core.types import LLMResponse
+from core.types import GeneratedQuestion, LLMResponse
 
 
 class TestLLMResponse:
@@ -42,10 +43,58 @@ class TestLLMResponse:
 
     def test_cache_hit_response_has_none_ttft(self) -> None:
         resp = LLMResponse(
-            content="cached", thinking="", model="m", provider="p",
-            prompt_tokens=0, completion_tokens=0, latency_ms=1,
-            ttft_ms=None, max_inter_token_ms=None, cache_hit=True, call_id="c",
+            content="cached",
+            thinking="",
+            model="m",
+            provider="p",
+            prompt_tokens=0,
+            completion_tokens=0,
+            latency_ms=1,
+            ttft_ms=None,
+            max_inter_token_ms=None,
+            cache_hit=True,
+            call_id="c",
         )
         assert resp.ttft_ms is None
         assert resp.max_inter_token_ms is None
         assert resp.cache_hit is True
+
+
+class TestGeneratedQuestion:
+    @pytest.fixture()
+    def sample_question(self) -> GeneratedQuestion:
+        return GeneratedQuestion(
+            question_id="719-1",
+            video_id="B7Hh0PY1kks",
+            task_type="Action Reasoning",
+            question="What are the differing motivations?",
+            options=("A. Option 1", "B. Option 2", "C. Option 3", "D. Option 4"),
+            answer="B",
+            source_nodes=(),
+            difficulty="medium",
+        )
+
+    def test_frozen_prevents_mutation(self, sample_question: GeneratedQuestion) -> None:
+        with pytest.raises(AttributeError):
+            sample_question.question = "篡改"
+
+    def test_all_fields_accessible(self, sample_question: GeneratedQuestion) -> None:
+        assert sample_question.question_id == "719-1"
+        assert sample_question.video_id == "B7Hh0PY1kks"
+        assert sample_question.task_type == "Action Reasoning"
+        assert sample_question.question == "What are the differing motivations?"
+        assert sample_question.options == (
+            "A. Option 1",
+            "B. Option 2",
+            "C. Option 3",
+            "D. Option 4",
+        )
+        assert sample_question.answer == "B"
+        assert sample_question.source_nodes == ()
+        assert sample_question.difficulty == "medium"
+
+    def test_options_is_tuple(self, sample_question: GeneratedQuestion) -> None:
+        assert isinstance(sample_question.options, tuple)
+
+    def test_source_nodes_is_tuple(self, sample_question: GeneratedQuestion) -> None:
+        assert isinstance(sample_question.source_nodes, tuple)