feat(api): 回忆录管线简化、路由延迟池与相关加固

- Phase1/2：移除 MemoirOrchestrator.run 与 process_memoir_segments 别名；文档改为 process_memoir_phase1。
- 槽位校验集中到 stage_constants（filter_stage_slots），批处理与顺序路径及 state_service 写库一致。
- StoryRoute：no_llm/parse_error/invalid_target 保守 new_story；短篇护栏不覆盖这些 fallback。
- Phase2 低置信单路径可选延迟（StoryPipelineResult.deferred）：不写 Chapter/Story，Segment 记录 defer 元数据，冷却内不重复消费；上限后停自动重试，Phase1 同类目新段唤醒池内段。
- Alembic 0017：segments 表 narrative_defer_* 列。
- ProfileAgent：经 LlmGateway/注入 Provider 统一聊天与 JSON，新增测试。
- ImagePromptOrchestrator：LLM 初始化失败可依配置降级或硬失败；补充策略测试。
- 配套单测与 README/本地开发文档表述更新。

Co-authored-by: Cursor <cursoragent@cursor.com>

api/app/features/memoir/story_pipeline_sync.py

@@ -11,6 +11,7 @@ import re
 import time
 import uuid
 from concurrent.futures import ThreadPoolExecutor
+from dataclasses import dataclass, field
 from typing import Any
 
 from sqlalchemy import func, select
@@ -20,6 +21,7 @@ from app.agents.memoir.narrative_agent import NarrativeAgent
 from app.agents.memoir.prompts import format_narrative_user_content
 from app.agents.memoir.story_route_agent import (
     APPEND_FIRST_CHAPTER_CATEGORIES,
+    FALLBACK_NEW_STORY_REASONS,
     PLAN_BATCH_MAX_SEGMENTS,
     StoryBatchPlan,
     StoryRouteAgent,
@@ -70,6 +72,23 @@ from app.features.story.sync_write import (
 logger = get_logger(__name__)
 
 
+@dataclass
+class StoryPipelineResult:
+    """Phase2 故事管线结果。
+
+    - 正常写入：``deferred=False``，``chapter`` 非空。
+    - 低置信延迟：``deferred=True``，``chapter`` 为 None；调用方应把 ``defer_segment_ids``
+      标记为延迟态，不要置 ``narrated/processed``，也不要触发后置任务。
+    """
+
+    chapter: Chapter | None
+    needs_cover: bool
+    dispatch_ids: set[str]
+    deferred: bool = False
+    defer_reason: str | None = None
+    defer_segment_ids: list[str] = field(default_factory=list)
+
+
 def _dialogue_lineage_dict_for_segment_ids(
     category_segments: list,
     segment_ids: list[str],
@@ -662,6 +681,7 @@ def _resolve_append_target(
         route_decision == "new_story"
         and chapter_category in APPEND_FIRST_CHAPTER_CATEGORIES
         and candidate_stories
+        and decision_source not in FALLBACK_NEW_STORY_REASONS
         and len(oral_norm)
         <= int(settings.memoir_story_route_append_guardrail_oral_chars)
     ):
@@ -952,9 +972,10 @@ def run_story_pipeline_for_category_batch(
     memoir_correlation_id: str | None = None,
     llm_fast: Any | None = None,
     memory_evidence: dict | None = None,
-) -> tuple[Chapter | None, bool, set[str]]:
-    """
-    返回 (chapter, needs_cover_enqueue, story_ids_to_dispatch_after_commit)。
+) -> StoryPipelineResult:
+    """运行某 chapter_category 的 Phase2 写入管线。
+
+    返回 :class:`StoryPipelineResult`。低置信路由会被延迟而不创建 Story/Chapter。
     """
     pipeline_phase_timings: dict[str, float] = {}
     narrative_agent = NarrativeAgent()
@@ -1074,8 +1095,46 @@ def run_story_pipeline_for_category_batch(
             valid_story_ids=valid_ids,
             story_meta=story_meta,
         )
+
+    single_route: Any = None
+    if plan is None:
+        single_route = route_agent.decide(
+            chapter_category=chapter_category,
+            chapter_title=title,
+            batch_transcript=route_transcript,
+            candidate_stories=candidates,
+            llm=llm_route,
+            valid_story_ids=valid_ids,
+            story_meta=story_meta,
+        )
     pipeline_phase_timings["route"] = time.perf_counter() - _t0
 
+    if (
+        plan is None
+        and single_route is not None
+        and single_route.reason in FALLBACK_NEW_STORY_REASONS
+        and bool(settings.memoir_route_defer_enabled)
+    ):
+        defer_ids = [str(s.id) for s in category_segments]
+        logger.info(
+            "event=memoir_pipeline_route_deferred memoir_correlation_id={} user_id={} "
+            "chapter_category={} segment_count={} reason={} "
+            "msg=Phase2 路由低置信，本批 segment 进入延迟池",
+            memoir_correlation_id or "",
+            user_id,
+            chapter_category,
+            len(defer_ids),
+            single_route.reason,
+        )
+        return StoryPipelineResult(
+            chapter=None,
+            needs_cover=False,
+            dispatch_ids=set(),
+            deferred=True,
+            defer_reason=str(single_route.reason),
+            defer_segment_ids=defer_ids,
+        )
+
     chapter = _ensure_chapter_record(
         session,
         user_id=user_id,
@@ -1110,17 +1169,12 @@ def run_story_pipeline_for_category_batch(
             fidelity_llm=llm_fidelity,
         )
     else:
-        route = route_agent.decide(
-            chapter_category=chapter_category,
-            chapter_title=title,
-            batch_transcript=route_transcript,
-            candidate_stories=candidates,
-            llm=llm_route,
-            valid_story_ids=valid_ids,
-            story_meta=story_meta,
+        route = single_route
+        decision_source = (
+            route.reason
+            if route.reason in FALLBACK_NEW_STORY_REASONS
+            else ("fallback_no_llm" if not llm_route else "single_decide")
         )
-
-        decision_source = "fallback_no_llm" if not llm else "single_decide"
         target_story_id, existing_for_narrative, decision_source = (
             _resolve_append_target(
                 session,
@@ -1191,4 +1245,8 @@ def run_story_pipeline_for_category_batch(
         timing_parts,
     )
 
-    return chapter, needs_cover, dispatch_ids
+    return StoryPipelineResult(
+        chapter=chapter,
+        needs_cover=needs_cover,
+        dispatch_ids=dispatch_ids,
+    )