feat(api): 访谈路径轻量门控、Memoir Phase1 批处理与叙事/记忆管线加固

- 新增 utterance_substance：短时/应答/元话语可跳过记忆检索、阶段 LLM 与资料抽取 LLM；可配置
- 输入归一化：LLM 模式默认仅语音/ASR；配置项写入 .env.example
- Memoir Phase1：可选 batch LLM 一次性抽取+分类（失败回退逐段）；Extraction 空槽位时阶段与 current_stage 对齐，prompt 约束收紧
- 叙事与忠实度：narrative_safety、证据重叠/场合锚点、标题 slots 与履历短语 grounded；fidelity 解析失败 fail-open 可配置
- 章节管线：锁 TTL 上调、锁竞争 Celery 重试、Phase2 immediate singleflight 等；story_pipeline_sync / chapter_compose / memoir_tasks 联动
- Memory：compaction / repo / summarizer / evidence 小修；事实 FTS 未命中是否回退最近事实可配置
- 新增 memoir_pipeline_trace；补充 memoir_reliability 文档与多项回归/门控测试

api/tests/test_fidelity_gate.py

@@ -0,0 +1,76 @@
+"""FidelityCheckAgent：解析/LLM 失败时的 fail-closed（新建叙事）vs fail-open（续写）。"""
+
+from __future__ import annotations
+
+from unittest.mock import MagicMock, patch
+
+import pytest
+
+from app.agents.memoir.fidelity_check_agent import FidelityCheckAgent
+from app.core.config import settings
+
+
+def test_fidelity_fail_closed_on_parse_when_not_append(
+    monkeypatch: pytest.MonkeyPatch,
+) -> None:
+    monkeypatch.setattr(settings, "memoir_fidelity_check_enabled", True)
+    monkeypatch.setattr(settings, "memoir_fidelity_fail_open_on_parse_error", False)
+    agent = FidelityCheckAgent()
+    llm = MagicMock()
+    with patch(
+        "app.agents.memoir.fidelity_check_agent.invoke_json_object",
+        side_effect=ValueError("simulated_bad_response"),
+    ):
+        assert (
+            agent.passes(
+                oral_text=" oral ",
+                narrative_json='{"paragraphs":[{"content":"x"}]}',
+                llm=llm,
+                is_append=False,
+            )
+            is False
+        )
+
+
+def test_fidelity_fail_open_on_parse_when_append(
+    monkeypatch: pytest.MonkeyPatch,
+) -> None:
+    monkeypatch.setattr(settings, "memoir_fidelity_check_enabled", True)
+    monkeypatch.setattr(settings, "memoir_fidelity_fail_open_on_parse_error", False)
+    agent = FidelityCheckAgent()
+    llm = MagicMock()
+    with patch(
+        "app.agents.memoir.fidelity_check_agent.invoke_json_object",
+        side_effect=ValueError("simulated_bad_response"),
+    ):
+        assert (
+            agent.passes(
+                oral_text=" oral ",
+                narrative_json='{"paragraphs":[{"content":"x"}]}',
+                llm=llm,
+                is_append=True,
+            )
+            is True
+        )
+
+
+def test_fidelity_fail_open_global_flag_overrides_append(
+    monkeypatch: pytest.MonkeyPatch,
+) -> None:
+    monkeypatch.setattr(settings, "memoir_fidelity_check_enabled", True)
+    monkeypatch.setattr(settings, "memoir_fidelity_fail_open_on_parse_error", True)
+    agent = FidelityCheckAgent()
+    llm = MagicMock()
+    with patch(
+        "app.agents.memoir.fidelity_check_agent.invoke_json_object",
+        side_effect=ValueError("simulated_bad_response"),
+    ):
+        assert (
+            agent.passes(
+                oral_text=" oral ",
+                narrative_json='{"paragraphs":[{"content":"x"}]}',
+                llm=llm,
+                is_append=False,
+            )
+            is True
+        )