fix:

1. 修复安卓部分机型顶部安全区遮挡回忆录标题的问题；
2. 降低封面图生成阈值和展示逻辑，独立封面图未生成时，使用正文图；
3. 去掉“嗯。”生硬回答，去掉不合理段首承接词；
4. 新增章节封面所需最少插图数的配置项

api/app/tasks/chapter_cover_enqueue.py

@@ -18,6 +18,7 @@ from app.features.memoir.cover_eligibility import (
     chapter_eligible_for_cover_by_inline_body_image_count,
     chapter_has_story_links,
     chapter_needs_cover_enqueue,
+    effective_chapter_markdown_for_cover_gates,
     primary_chapter_memoir_image,
 )
 from app.features.memoir.models import Chapter, ChapterStoryLink
@@ -42,14 +43,13 @@ def _chapter_eligible_for_http_enqueue(chapter: Chapter | None) -> bool:
         return False
     if getattr(chapter, "cover_asset_id", None):
         return False
-    md = (chapter.canonical_markdown or "").strip()
-    body = md or ""
-    if not body.strip():
-        return False
-    body = strip_image_placeholders(body).strip()
+    view = effective_chapter_markdown_for_cover_gates(chapter)
+    body = strip_image_placeholders(view).strip()
     if not body:
         return False
-    if not chapter_eligible_for_cover_by_inline_body_image_count(chapter):
+    if not chapter_eligible_for_cover_by_inline_body_image_count(
+        chapter, markdown=view
+    ):
         return False
     cover_rec = primary_chapter_memoir_image(chapter)
     if cover_rec and (cover_rec.status or "").strip() == "completed":
@@ -58,7 +58,7 @@ def _chapter_eligible_for_http_enqueue(chapter: Chapter | None) -> bool:
 
 
 def _chapter_eligible_for_pipeline_enqueue(chapter: Chapter | None) -> bool:
-    """尚无 cover_asset、正文插图数 > 3（与 HTTP 闸门共用 chapter_needs_cover_enqueue 核心）。"""
+    """尚无 cover_asset、正文插图数达 MEMOIR_MIN_INLINE_IMAGES_FOR_CHAPTER_COVER（与 HTTP 闸门共用）。"""
     return bool(chapter_needs_cover_enqueue(chapter))