fix(books): 泥潭策展语与回退契约实现；自托管仓星标语义

- BooksPage 实现 schema 注释承诺的 description 回退（正文首段去记号
  取 60 字）——视觉复核抓到的"文档说了代码没做"缺口
- 泥潭补人工策展语（回退之上）；自托管仓星标改 self-hosted 徽标
  （gitea 无 star 真值，★0 语义突兀——视觉复核次要备注）

验证: build 28 页 exit 0；dist/books 含泥潭策展语；dist/opensource
      self-hosted 徽标与 ★57 并存实测

Spec: 2026-10-25_add-terminal-books-admin

Co-authored-by: GLM-5.3

public/admin/config.yml

@@ -27,7 +27,8 @@ collections:
     public_folder: ''
     summary: '{{fields.group}} · {{fields.title}}'
     fields:
-      - { label: 标题, name: title, widget: string, required: false }
+      # title 必填：Astro schema z.string() 无 .optional()，omit 纪律下必需且有值才会落键（空 title 会让 main 不可构建）
+      - { label: 标题, name: title, widget: string, required: true }
       - { label: 图片, name: image, widget: image }
       - { label: 分组, name: group, widget: select, options: [street, landscape] }
       - { label: 替代文本, name: alt, widget: string, required: false }