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/graph/LinkGraph.tsx

@@ -123,7 +123,7 @@ export function LinkGraph({ onSwitchToEditor }: { onSwitchToEditor?: () => void
 
   return (
     <div style={{ flex: 1, background: 'var(--bg-secondary)', position: 'relative', overflow: 'hidden' }}>
-      <svg ref={svgRef} style={{ position: 'absolute', inset: 0, width: '100%', height: '100%' }} />
+      <svg data-testid="graph-canvas" ref={svgRef} style={{ position: 'absolute', inset: 0, width: '100%', height: '100%' }} />
       {/* FR-G4：画布控件 */}
       <div data-testid="graph-controls" style={{ position: 'absolute', bottom: 12, right: 12, display: 'flex', flexDirection: 'column', gap: 4, zIndex: 10 }}>
         <button title="放大" onClick={() => zoomBy(1.3)} style={ctrlBtn}>+</button>