feat(creator-studio): two-row masthead with site logo and user avatar

顶栏改为知乎式两行结构：第一行左侧站点 LOGO、右侧当前用户头像，
第二行只保留正文工具条并居中，同时移除「Jio / 写文章」字样。

- bootstrap payload 新增 site/viewer 身份字段（复用 jio_get_site_logo_url
  与 jio_get_avatar_url，前端不拼 URL、不做权限判断）
- 拆分 draft 类型、TinyMCE 块运行时、顶栏组件，index.tsx 1065 → 735 行
- 清理死代码：未调用的 keepCaretInsideCode、永远无法打开的代码语言弹窗
  （setCodeLanguage 只会收到 null，codeTargetRef 从未赋值）及其样式，
  以及顶栏移除后失效的 bar-left/brand/mode/save-draft/ghost/primary 规则
- 契约测试、本地预览与截图脚本同步到新 DOM

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

assets/creator-studio/scripts/shoot.cjs

@@ -55,14 +55,16 @@ const PREFIX = process.argv[3] || 'C:/Users/Xing/Desktop/WP-Date/data/wordpress/
         };
       };
       return {
+        masthead: pick('.jio-creator__masthead'),
+        brandLogo: pick('.jio-creator__brand-logo'),
+        avatar: pick('.jio-creator__me-avatar'),
         bar: pick('.jio-creator__bar'),
         title: pick('.jio-creator__title textarea'),
         settings: pick('.jio-creator__settings'),
         canvas: pick('.jio-creator__canvas'),
         toolbar: pick('.jio-creator__toolbar-tools'),
         editor: pick('.jio-creator__editor .mce-edit-area'),
-        primaryBtn: pick('.jio-creator__primary'),
-        ghostBtn: pick('.jio-creator__ghost'),
+        publishBtn: pick('.jio-creator__status-primary'),
         pageBg: getComputedStyle(document.body).backgroundColor,
       };
     });