refactor(agents): 抽取阶段常量与对话上下文；快档 LLM；图片 prompt 可禁止回退

访谈与阶段
- 新增 app/agents/stage_constants.py：集中 CHAT_STAGES、章节分类/顺序、阶段到默认 memoir 类别等，与 MemoirState 默认槽位顺序对齐；减少散落在 prompts 内的重复常量。
- 新增 app/agents/chat/prompt_context.py：以 ChatPromptContext 汇总 guided 系统提示所需字段（阶段、槽位、轮次、人设、记忆证据、回复长度模式、背景声线、职业等），统一走 get_guided_conversation_prompt。
- 大幅收敛 app/agents/chat/prompts_conversation.py；调整 prompts.py、stage_prompts.py、stage_detection.py；同步 interview_agent、profile_agent、helpers 与 state_schema，使对话侧构造提示的方式一致、可测。

回忆录流水线
- memoir/prompts.py 删除已迁至 stage_constants / 独立模板的大段常量与图片占位相关逻辑；classification / extraction / fidelity / narrative agents 与 orchest（全量历史仍可用于计数，注入模型时按轮次与字符上限截断）、image_prompt_fallback_disabled。
- dependencies 增加 get_llm_provider_fast（LRU 缓存，可与默认共用密钥与 base_url）。

任务与编排
- memoir_tasks：prepare_batches 注入 llm_fast；开启独立快档模型时打结构化日志。
- chapter_cover_tasks、story_image_tasks：与图片 prompt / JSON 工具路径或策略变更对齐（import 与行为一致）。
- story_pipeline_sync 等小处同步。

其它核心
- langchain_llm、text_normalize 随上述调用链微调。

开发者体验
- .cursor/settings.json：启用 redis-development、postman 插件。

测试
- 新增 test_image_prompt_policy：覆盖「禁止回退」等图片 prompt 策略。
- 更新 test_interview_prompts、test_interview_reply_length、test_experience_regressions、test_json_and_memory_utils，匹配新常量位置、json_utils 与对话/长度行为。

api/app/features/memoir/memoir_images/image_placeholder_template.py

@@ -0,0 +1,9 @@
+"""Shared image style template for story/chapter image tasks (decoupled from narrative prompts)."""
+
+IMAGE_PLACEHOLDER_TEMPLATE = (
+    "温暖怀旧风格，年代感复古色调，柔和光影，朴素温馨氛围，安静治愈，低饱和度，"
+    "质感柔和细腻，简约构图，充满岁月沉淀感与故事感，高清唯美插画封面，不要包含文字，"
+    "要适合老年人审美，画面要真实可信、让老年人产生共鸣与代入感，"
+    "场景环境、建筑风格、服饰器物必须严格符合所述时代背景和地域特色，"
+    "有朦胧怀旧的年代感。"
+)

api/app/features/memoir/memoir_images/json_payload.py

@@ -1,23 +0,0 @@
-import re
-
-_MARKDOWN_JSON_FENCE_RE = re.compile(
-    r"^\s*```(?:json)?\s*(.*?)\s*```\s*$",
-    re.IGNORECASE | re.DOTALL,
-)
-
-
-def extract_json_payload(raw_response: str | None) -> str:
-    cleaned = (raw_response or "").strip()
-    fenced_match = _MARKDOWN_JSON_FENCE_RE.match(cleaned)
-    if fenced_match:
-        cleaned = fenced_match.group(1).strip()
-
-    if cleaned.startswith("{") and cleaned.endswith("}"):
-        return cleaned
-
-    start = cleaned.find("{")
-    end = cleaned.rfind("}")
-    if start != -1 and end != -1 and end > start:
-        return cleaned[start : end + 1].strip()
-
-    return cleaned

api/app/features/memoir/memoir_images/parser.py

@@ -4,7 +4,7 @@ from typing import Any
 
 from app.features.memoir.asset_resolver import strip_image_placeholders
 
-from .json_payload import extract_json_payload
+from app.core.json_utils import extract_json_payload
 from .schema import IMAGE_STATUS_PENDING
 
 PLACEHOLDER_RE = re.compile(

api/app/features/memoir/memoir_images/prompting.py

@@ -2,10 +2,11 @@ import json
 import re
 from typing import Any, Optional
 
+from app.core.config import settings
 from app.core.langchain_llm import invoke_json_object
 from app.core.logging import get_logger
 
-from .json_payload import extract_json_payload
+from app.core.json_utils import extract_json_payload
 from .settings import MemoirImageSettings
 
 logger = get_logger(__name__)
@@ -83,12 +84,19 @@ class MemoirImagePromptService:
                     "prompt_context": prompt_context,
                 }
             except Exception as exc:
+                if settings.image_prompt_fallback_disabled:
+                    raise
                 logger.warning(
                     "图片 prompt 生成回退到默认模板: chapter_category={}, title={}, error={}",
                     chapter_category,
                     chapter_title,
                     exc,
                 )
+        elif settings.image_prompt_fallback_disabled:
+            raise RuntimeError(
+                "MemoirImagePromptService.build_prompt requires LLM when "
+                "image_prompt_fallback_disabled is True"
+            )
 
         return {
             "prompt": _ensure_style_in_prompt(
@@ -112,6 +120,13 @@ class MemoirImagePromptService:
         context_excerpt: str,
     ) -> dict[str, str]:
         """生成章节封面图的 image-generation prompt。"""
+        excerpt = (context_excerpt or "").strip()
+        if settings.image_prompt_fallback_disabled and not excerpt:
+            raise RuntimeError(
+                "Chapter cover prompt requires non-empty context_excerpt when "
+                "image_prompt_fallback_disabled is True"
+            )
+
         style = self.CATEGORY_STYLE_MAP.get(
             chapter_category, self.settings.default_style
         )
@@ -120,7 +135,7 @@ class MemoirImagePromptService:
         llm_input = {
             "chapter_title": chapter_title,
             "chapter_category": chapter_category,
-            "context_excerpt": context_excerpt,
+            "context_excerpt": excerpt,
             "default_style": style,
             "default_size": self.settings.default_size,
         }
@@ -150,18 +165,25 @@ class MemoirImagePromptService:
                     "prompt_context": prompt_context,
                 }
             except Exception as exc:
+                if settings.image_prompt_fallback_disabled:
+                    raise
                 logger.warning(
                     "封面 prompt 生成回退到默认模板: chapter_category={}, title={}, error={}",
                     chapter_category,
                     chapter_title,
                     exc,
                 )
+        elif settings.image_prompt_fallback_disabled:
+            raise RuntimeError(
+                "MemoirImagePromptService.build_cover_prompt requires LLM when "
+                "image_prompt_fallback_disabled is True"
+            )
 
         return {
             "prompt": _ensure_style_in_prompt(
                 self._build_cover_fallback_prompt(
                     chapter_category=chapter_category,
-                    context_excerpt=context_excerpt,
+                    context_excerpt=excerpt,
                     style=style,
                 ),
                 style,
@@ -171,6 +193,105 @@ class MemoirImagePromptService:
             "prompt_context": prompt_context,
         }
 
+    def build_story_primary_prompt(
+        self,
+        story_title: str,
+        story_stage: str | None,
+        prompt_brief: str,
+        style_profile: str | None,
+    ) -> dict[str, str]:
+        """生成 story 主插图的 image-generation prompt（LLM / fallback 策略与章节配图一致）。
+
+        `story_stage` 与 `Story.stage` 一致：通常为章节 category（如 career_early），也可能为
+        访谈五阶段名（childhood/career/…）；二者都参与默认画风推断。
+        """
+        from app.agents.stage_constants import STAGE_TO_DEFAULT_CATEGORY
+
+        brief = (prompt_brief or "").strip()
+        if settings.image_prompt_fallback_disabled and not brief:
+            raise RuntimeError(
+                "Story image prompt requires non-empty prompt_brief when "
+                "image_prompt_fallback_disabled is True"
+            )
+
+        stage_key = (story_stage or "").strip()
+        if stage_key in self.CATEGORY_STYLE_MAP:
+            cat = stage_key
+        else:
+            cat = STAGE_TO_DEFAULT_CATEGORY.get(stage_key, "summary")
+        explicit_style = (style_profile or "").strip()
+        style = explicit_style or self.CATEGORY_STYLE_MAP.get(
+            cat, self.settings.default_style
+        )
+        prompt_context = f"story:{stage_key}:{story_title}"
+
+        llm_input = {
+            "story_title": story_title,
+            "story_stage": stage_key,
+            "prompt_brief": brief,
+            "default_style": style,
+            "default_size": self.settings.default_size,
+        }
+
+        if self.llm:
+            try:
+                prompt_text = (
+                    "Return JSON only with keys prompt, style, size. "
+                    "Convert into an image-generation prompt for the PRIMARY hero illustration "
+                    "of a personal memoir story (one focal scene, emotionally resonant). "
+                    "The API uses response_format=json_object.\n"
+                    + json.dumps(llm_input, ensure_ascii=False)
+                )
+                raw_response = invoke_json_object(
+                    self.llm,
+                    prompt_text,
+                    max_tokens=512,
+                    agent="MemoirImagePromptService.build_story_primary_prompt",
+                )
+                parsed = json.loads(extract_json_payload(raw_response))
+                return {
+                    "prompt": _ensure_style_in_prompt(
+                        parsed["prompt"], parsed.get("style", style)
+                    ),
+                    "style": parsed.get("style", style),
+                    "size": parsed.get("size", self.settings.default_size),
+                    "prompt_context": prompt_context,
+                }
+            except Exception as exc:
+                if settings.image_prompt_fallback_disabled:
+                    raise
+                logger.warning(
+                    "story 主图 prompt 生成回退到默认模板: stage={}, title={}, error={}",
+                    story_stage,
+                    story_title,
+                    exc,
+                )
+        elif settings.image_prompt_fallback_disabled:
+            raise RuntimeError(
+                "MemoirImagePromptService.build_story_primary_prompt requires LLM when "
+                "image_prompt_fallback_disabled is True"
+            )
+
+        from .image_placeholder_template import IMAGE_PLACEHOLDER_TEMPLATE
+
+        if brief:
+            body = brief
+        else:
+            joined = "，".join(
+                filter(
+                    None,
+                    [(story_title or "").strip(), stage_key or None],
+                )
+            )
+            body = joined or "人生故事"
+        prompt_line = f"{IMAGE_PLACEHOLDER_TEMPLATE}。{body}"
+        return {
+            "prompt": _ensure_style_in_prompt(prompt_line, style),
+            "style": style,
+            "size": self.settings.default_size,
+            "prompt_context": prompt_context,
+        }
+
     def _build_cover_fallback_prompt(
         self,
         chapter_category: str,