feat(api): 统一 LLM JSON 调用层 llm_json_call，按域 Schema 迁移 chat/memoir agents

api/app/agents/memoir/narrative_agent.py

@@ -5,7 +5,6 @@ NarrativeAgent：生成创意标题和叙事改写。
 
 from __future__ import annotations
 
-import json
 from typing import Any, Dict, Optional
 
 from app.agents.stage_constants import CHAPTER_CATEGORIES
@@ -14,9 +13,11 @@ from app.agents.memoir.prompts import (
     get_narrative_json_prompt,
     get_narrative_merge_json_prompt,
 )
+from app.agents.memoir.schemas import MemoirTitleOutput
+from app.core.config import settings
 from app.core.langchain_llm import invoke_json_object
+from app.core.llm_call import llm_json_call
 from app.core.logging import get_logger
-from app.core.json_utils import extract_json_payload
 
 logger = get_logger(__name__)
 
@@ -44,17 +45,23 @@ class NarrativeAgent:
                 user_profile=user_profile,
                 birth_year=birth_year,
             )
-            raw = invoke_json_object(
+            default_title = f"{CHAPTER_CATEGORIES.get(stage, stage)} 回忆"
+
+            def _title_fallback() -> MemoirTitleOutput:
+                return MemoirTitleOutput(title=default_title)
+
+            out = llm_json_call(
                 llm,
                 prompt,
-                max_tokens=256,
+                MemoirTitleOutput,
+                max_tokens=settings.memoir_title_max_tokens,
                 agent="NarrativeAgent.generate_title",
+                fallback_factory=_title_fallback,
             )
-            data = json.loads(extract_json_payload(raw))
-            title = (data.get("title") or "").strip() if isinstance(data, dict) else ""
+            title = (out.title or "").strip()
             if title:
                 return title.strip('"')
-            return f"{CHAPTER_CATEGORIES.get(stage, stage)} 回忆"
+            return default_title
         except Exception as e:
             logger.warning("NarrativeAgent 生成标题失败: {}", e)
             return f"{CHAPTER_CATEGORIES.get(stage, stage)} 回忆"
@@ -100,7 +107,7 @@ class NarrativeAgent:
                     background_voice=background_voice,
                     occupation=occupation,
                 )
-                max_tokens = 8192
+                max_tokens = int(settings.memoir_narrative_merge_max_tokens)
                 agent_name = "NarrativeAgent.generate_narrative_merge"
             else:
                 prompt = get_narrative_json_prompt(
@@ -113,7 +120,7 @@ class NarrativeAgent:
                     background_voice=background_voice,
                     occupation=occupation,
                 )
-                max_tokens = 4096
+                max_tokens = int(settings.memoir_narrative_max_tokens)
                 agent_name = "NarrativeAgent.generate_narrative"
             return invoke_json_object(
                 llm,