feat: M5 透明窗+亚克力（FR-A2，BrowserWindow transparent/backgroundMaterial=acrylic，App 根用 var(--bg-primary)，透明主题透出亚克力）

apps/desktop/src/renderer/App.tsx

@@ -43,7 +43,7 @@ export function App() {
   // 编辑器样式随设置生效（FR-编辑器设置真实生效）
   useEffect(() => { document.documentElement.style.setProperty('--editor-font-size', settings.fontSize + 'px'); document.documentElement.style.setProperty('--editor-font-family', settings.fontFamily); document.documentElement.style.setProperty('--editor-white-space', settings.wordWrap ? 'pre-wrap' : 'pre'); }, [settings.fontSize, settings.fontFamily, settings.wordWrap]);
   return (
-    <div style={{ display: 'flex', flexDirection: 'column', height: '100vh', background: '#1a1a1a', color: '#ddd' }}>
+    <div style={{ display: 'flex', flexDirection: 'column', height: '100vh', background: 'var(--bg-primary, #1a1a1a)', color: '#ddd' }}>
       <TitleBar view={view} onToggleView={() => setView(v => v === 'editor' ? 'graph' : 'editor')} onSettings={() => setShowSettings(true)} onAppearance={() => setShowAppearance(true)} onToggleSidebar={() => layout.toggleSidebar()} onToggleMinimal={() => layout.toggleMinimal()} minimal={layout.minimal} />
       <Toolbar />
       {view === 'editor' && <TabBar />}