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

src/components/geek/ProjectWall.astro

@@ -39,7 +39,7 @@ try {
                 {p.language}
               </span>
             )}
-            <span class="stars">★ {p.stars}</span>
+            <span class="stars">{p.source === 'gitea' ? 'self-hosted' : `★ ${p.stars}`}</span>
           </span>
         </a>
       </li>