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/app/agents/memoir/extraction_agent.py

@@ -64,15 +64,21 @@ class ExtractionAgent:
                 agent="ExtractionAgent.extract",
             )
             parsed = json.loads(extract_json_payload(raw))
-            raw_detected = parsed.get("detected_stage", detected_stage)
-            detected_stage = normalize_chat_stage(
-                str(raw_detected) if raw_detected is not None else None,
-                fallback=current_stage,
-            )
             raw_slots = parsed.get("slots", {}) or {}
             extracted_slots = {
                 k: v if isinstance(v, str) else str(v) for k, v in raw_slots.items()
             }
+            if not extracted_slots:
+                # 无实质 slot 时不推断阶段，避免元话语被标成任意 childhood 等（与服务端护栏一致）
+                detected_stage = normalize_chat_stage(
+                    current_stage, fallback=current_stage
+                )
+            else:
+                raw_detected = parsed.get("detected_stage", current_stage)
+                detected_stage = normalize_chat_stage(
+                    str(raw_detected) if raw_detected is not None else None,
+                    fallback=current_stage,
+                )
         except (json.JSONDecodeError, Exception) as e:
             logger.warning("ExtractionAgent LLM 解析失败: {}", e)