feat(api): 叙事 prompt、职业上下文、读路径章节、WS 解耦与错误脱敏

- 回忆录：事实边界补充允许清单；传记文体示例与 JSON 叙事要求对齐
- default 职业提示 occupation_context；cadre/military 退休语境
- GET 章节读路径零写入，prepare_chapter_read_view + markdown_for_response
- 文本归一抽到 core/text_normalize；移除弃用 reply 策略与 recompose_chapters_for_story
- ConversationService：WS 连接/用户段落/结束对话；对外错误固定文案
- 测试：HTTP 脱敏契约、章节读视图、occupation 与 background_voice

api/app/features/memoir/reading_segment_materialize.py

@@ -65,8 +65,12 @@ def chapter_body_meets_minimum_for_display(canonical_markdown: str) -> bool:
     )
 
 
-def chapter_meets_minimum_display(ch: Any) -> bool:
-    """基于章节当前 canonical_markdown（物化后）判断是否可对读者展示。"""
+def chapter_meets_minimum_display(
+    ch: Any, *, canonical_markdown_override: str | None = None
+) -> bool:
+    """基于章节 canonical（或读路径临时物化串）判断是否可对读者展示。"""
+    if canonical_markdown_override is not None:
+        return chapter_body_meets_minimum_for_display(canonical_markdown_override)
     md = getattr(ch, "canonical_markdown", None) or ""
     return chapter_body_meets_minimum_for_display(str(md))