feat(api+app): 对话阶段化、回忆录流水线与客户端会话体验

- DB: segments 用户输入文本（Alembic 0002）
- Chat: 阶段检测/阶段提示/回复限制，编排与访谈/画像 prompts 调整
- Memoir: 忠实度检查 agent，叙事与分类等链路更新
- Core: agent 日志、Alembic 启动、LangChain/日志/配置等
- Story: time_hints；Memory 检索与相关测试
- Expo: 助手头像、会话页与消息拆分、实时会话与文案/i18n
- Docs/scripts/tests: 迁移脚本、LLM JSON/记忆检索文档、新增单测

api/app/agents/memoir/story_route_agent.py

@@ -13,7 +13,7 @@ from app.agents.memoir.prompts import (
     get_story_batch_plan_prompt,
     get_story_route_prompt,
 )
-from app.core.langchain_llm import bind_json_object_mode
+from app.core.langchain_llm import invoke_json_object
 from app.core.logging import get_logger
 from app.features.story.models import Story
 
@@ -90,7 +90,7 @@ def _build_candidate_json(stories: list[Story], *, preview_chars: int = 220) ->
 def _build_segments_json_for_plan(
     segments: list[tuple[str, str]], *, text_preview_chars: int = 4000
 ) -> str:
-    """segments: (id, transcript_text) 按口述顺序。"""
+    """segments: (id, user_input_text) 按口述顺序。"""
     rows: list[dict[str, str]] = []
     for sid, text in segments:
         t = (text or "").strip()
@@ -157,13 +157,16 @@ class StoryRouteAgent:
             candidate_stories_json=payload,
         )
         try:
-            json_llm = bind_json_object_mode(llm, max_tokens=1024)
-            response = json_llm.invoke(prompt)
-            raw = (response.content or "").strip()
+            raw = invoke_json_object(
+                llm,
+                prompt,
+                max_tokens=1024,
+                agent="StoryRouteAgent.decide",
+            ).strip()
             data = json.loads(raw)
             decision = StoryRouteDecision.model_validate(data)
         except Exception as e:
-            logger.warning("StoryRouteAgent 解析失败: %s", e)
+            logger.warning("StoryRouteAgent 解析失败: {}", e)
             return StoryRouteDecision(
                 decision="new_story",
                 new_story_title=None,
@@ -174,7 +177,7 @@ class StoryRouteAgent:
             tid = decision.target_story_id
             if not tid or tid not in valid_story_ids:
                 logger.warning(
-                    "StoryRoute append 无效 target_story_id=%s，回退 new_story",
+                    "StoryRoute append 无效 target_story_id={}，回退 new_story",
                     tid,
                 )
                 return StoryRouteDecision(
@@ -212,18 +215,21 @@ class StoryRouteAgent:
             candidate_stories_json=payload,
         )
         try:
-            json_llm = bind_json_object_mode(llm, max_tokens=4096)
-            response = json_llm.invoke(prompt)
-            raw = (response.content or "").strip()
+            raw = invoke_json_object(
+                llm,
+                prompt,
+                max_tokens=4096,
+                agent="StoryRouteAgent.plan_batch",
+            ).strip()
             data = json.loads(raw)
             plan = StoryBatchPlan.model_validate(data)
         except Exception as e:
-            logger.warning("StoryRouteAgent.plan_batch 解析失败: %s", e)
+            logger.warning("StoryRouteAgent.plan_batch 解析失败: {}", e)
             return None
 
         ordered = [s[0] for s in segments]
         ok, err = validate_story_batch_plan(ordered, plan, valid_story_ids)
         if not ok:
-            logger.warning("StoryRouteAgent.plan_batch 校验失败: %s", err)
+            logger.warning("StoryRouteAgent.plan_batch 校验失败: {}", err)
             return None
         return plan