fix: route None/degraded diagnoses to lapse; abort on high degrade rate

tests/unit/test_diagnose.py

@@ -17,6 +17,7 @@ from unittest.mock import AsyncMock, MagicMock
 import pytest
 
 from core.evolution.diagnose import (
+    _build_skill_case_packs,
     _percentile,
     _trigrams,
     aggregate_d2,
@@ -43,6 +44,7 @@ from core.evolution.types import (
     CaseSample,
     DiagnosePrompts,
     DiagnosisResult,
+    ErrorAttribution,
     QuestionMetrics,
     SkillStepAdherence,
     SpanMetrics,
@@ -771,3 +773,52 @@ class TestRunDiagnosis:
         assert result.run_id == "run1"
         assert result.error_attributions == []
         assert result.degraded_count == 0
+
+
+class TestBuildSkillCasePacksDegradeRouting:
+    """_build_skill_case_packs 降级/未判定分流：仅 defect 且非 degraded 进正文路径。"""
+
+    def test_none_cause_and_degraded_route_to_lapse(self) -> None:
+        """cause_category=None（判别失败）与 degraded 题按 lapse 处置，不进 defect 正文路径。"""
+        tt = "Action Reasoning"
+        qm_none = _make_qm(question_id="q-none", task_type=tt, correct=False, degraded=False)
+        qm_degraded = _make_qm(question_id="q-deg", task_type=tt, correct=False, degraded=True)
+        # 补两道正确题，避免退化
+        qm_ok1 = _make_qm(question_id="q-ok1", task_type=tt, correct=True)
+        qm_ok2 = _make_qm(question_id="q-ok2", task_type=tt, correct=True)
+        metrics = [qm_none, qm_degraded, qm_ok1, qm_ok2]
+
+        attributions = [
+            # 判别失败：cause_category=None
+            ErrorAttribution(
+                question_id="q-none",
+                error_type="reasoning",
+                reasoning_failure_type=None,
+                cause_category=None,
+                lapse_note="复核该类推理规则",
+            ),
+            # degraded 题即便被判 defect，也须走 lapse（不驱动正文进化）
+            ErrorAttribution(
+                question_id="q-deg",
+                error_type="reasoning",
+                reasoning_failure_type=None,
+                cause_category="defect",
+                lapse_note=None,
+            ),
+        ]
+
+        packs = _build_skill_case_packs(
+            all_metrics=metrics,
+            error_attributions=attributions,
+            traces_by_question={},
+            predictions=[],
+            d3_stats={},
+            d4_stats={},
+        )
+
+        pack = packs[tt]
+        failure_ids = {c.question_id for c in pack.failure_cases}
+        assert "q-none" not in failure_ids
+        assert "q-deg" not in failure_ids
+        # None-cause 的 lapse_note 应被收进 lapse_notes
+        assert any("复核该类推理规则" in n for n in pack.lapse_notes)