feat(blog): wire root barrel (entity types + ui query helpers)

packages/blog/src/index.ts

@@ -1 +1,3 @@
-export {};
+export type { Article, ArticleStatus } from "./entities/article";
+export { ArticleNotFoundError, InputParseError } from "./entities/errors";
+export { articleBySlugQuery, listArticlesQuery } from "./ui/query";