ui: 统一图标系统/字体/文案/token，标题栏与状态栏重做，编辑器排版打磨，窗口边框设计

apps/desktop/src/renderer/features/editor/Editor.tsx

@@ -1,6 +1,7 @@
 import { useStore } from '../../store';
 import { TiptapEditor } from './TiptapEditor';
 import { MoreActions } from './MoreActions';
+import { BookOpen } from 'lucide-react';
 import type { SaveState } from '../../store';
 
 function saveLabel(s: SaveState): string {
@@ -14,9 +15,14 @@ export function Editor() {
   const title = useStore(s => s.title);
   const saveState = useStore(s => s.saveState);
   if (!currentPath) {
+    // B档-8：空状态引导
     return (
-      <div style={{ flex: 1, display: 'flex', alignItems: 'center', justifyContent: 'center', opacity: 0.4 }}>
-        <div style={{ textAlign: 'center' }}>从左侧选择一篇笔记，或新建文档开始</div>
+      <div style={{ flex: 1, display: 'flex', alignItems: 'center', justifyContent: 'center' }}>
+        <div style={{ textAlign: 'center', color: 'var(--text-tertiary)' }}>
+          <div style={{ marginBottom: 14, opacity: 0.55 }}><BookOpen size={42} strokeWidth={1.4} /></div>
+          <div style={{ fontSize: 15, color: 'var(--text-secondary)', marginBottom: 6 }}>从左侧选择一篇笔记，或新建文档开始</div>
+          <div style={{ fontSize: 12, opacity: 0.7 }}>支持 Markdown · 代码高亮 · 公式 · 知识图谱</div>
+        </div>
       </div>
     );
   }