Expose Studio cover rendering API and add three source-based layout tools

apps/studio/src/content/ideas.ts

@@ -1,8 +1,8 @@
 import ref17 from './templates/ref-17.json';
 export type Slide={heading:string;body:string;color:string;key?:string;label?:string;accent?:string;kicker?:string};
-export type Idea={slug:string;title:string;summary:string;slides:Slide[];template?:typeof ref17};
+export type Idea={slug:string;title:string;summary:string;slides:Slide[];tool?:string;template?:typeof ref17};
 // Studio owns creative pages. Wiki source tutorials are consumed as text/image data.
-export const ideas:Idea[]=[{
+export const ideas:Idea[]=[{slug:'layout-selection',tool:'layout-selection',title:'三种排版 · 模板选择工具',summary:'ref-01、ref-07、ref-26 三种不同构图的可编辑试版。',slides:[]},{
  slug:'learning-skills-template',title:'学习资料合集 · 封面模板试版',
  summary:'一张空白母版与三张主题占位封面，共用 ref-17 的同一套构件坐标；先试文案、色调和边界，暂不填具体 Skills。',template:ref17,
  slides:[

apps/studio/src/content/tool-links.ts

@@ -0,0 +1,2 @@
+// Stable Wiki post ID; the tutorial is published through /api/posts, never registered as a Wiki route.
+export const tutorialPost='/explore/9ebd8f78d54b4b9db741b4e8';