feat(studio/articles): Dimzou draft preview

Adds a 预览 action (enabled once an article has a Dimzou document) opening a
sheet that fetches and renders the draft — cover, title, summary, and body HTML
(typography/prose). Re-enables the @tailwindcss/typography plugin for prose.

src/api/modules/studio.ts

@@ -36,6 +36,20 @@ export const fetchStylePresets = (params: ListParams) =>
 export const updateRobotAuthor = (id: string, payload: Partial<StudioRobotAuthor>) =>
   api.put<ApiResponse<StudioRobotAuthor>>(`${BASE}/robot-authors/${id}`, payload)
 
+export interface ArticlePreview {
+  kind: 'studio_article_preview'
+  article_id: string
+  version_status: 'draft' | 'published' | null
+  title: string | null
+  summary: string | null
+  cover_image: { url: string; alt?: string | null } | null
+  body_html: string
+  has_content: boolean
+}
+
+export const fetchArticlePreview = (id: string) =>
+  api.get<ApiResponse<ArticlePreview>>(`${BASE}/articles/${id}/preview`)
+
 // ---- agent tokens (show-once) ----
 
 export const fetchAgentTokens = () =>