feat: macOS 改用原生圆角与原生红绿灯

- tauri.conf.json: decorations=true + titleBarStyle=Overlay + transparent
  + hiddenTitle + trafficLightPosition，启用原生圆角/squircle 与原生红绿灯
- main.css: 移除 #root 的 CSS border-radius，避免圆弧覆盖原生连续曲率
- App.tsx: macOS 下隐藏自绘 Windows 风格三按钮
- ContentArea.tsx: 侧栏隐藏（沉浸/竖屏）时 header 左侧为红绿灯留白
- Sidebar.tsx: macOS 下 logo 区上内边距增大，避开红绿灯

Co-Authored-By: Claude <noreply@anthropic.com>

src/components/ContentArea.tsx

@@ -104,6 +104,12 @@ export function ContentArea({
   bottomInset = 0,
 }: ContentAreaProps): React.JSX.Element {
   const { t } = useTranslation()
+  const isMacOS =
+    typeof navigator !== "undefined" &&
+    /mac/i.test(navigator.userAgent) &&
+    !/iphone|ipad|ipod|android/i.test(navigator.userAgent)
+  // macOS 使用原生红绿灯，侧栏隐藏（沉浸/竖屏）时顶部左侧需为红绿灯留白
+  const macTrafficLightsInset = isMacOS && (isPortraitMode || immersiveMode)
   const location = useLocation()
   const navigate = useNavigate()
   const isSubPage = location.pathname !== "/" && !location.pathname.startsWith("/home")
@@ -418,6 +424,7 @@ export function ContentArea({
             background: "var(--ss-header-bg)",
             borderBottom: "1px solid var(--ss-border-color)",
             flexShrink: 0,
+            paddingLeft: macTrafficLightsInset ? "80px" : 0,
             WebkitAppRegion: "drag",
             position: "relative",
           } as React.CSSProperties

src/components/Sidebar.tsx

@@ -213,13 +213,20 @@ export function Sidebar({
 
   const showFloatingPanel = floatingExpand && collapsed && floatingExpanded
 
+  const isMacOS =
+    typeof navigator !== "undefined" &&
+    /mac/i.test(navigator.userAgent) &&
+    !/iphone|ipad|ipod|android/i.test(navigator.userAgent)
+
   const renderSidebarBody = (isCollapsedView: boolean, hideMenu = false) => (
     <>
       <div
         data-tauri-drag-region
         style={
           {
-            padding: isCollapsedView ? "20px 8px 12px" : "24px 24px 16px",
+            padding: isCollapsedView
+              ? `${isMacOS ? 40 : 20}px 8px 12px`
+              : `${isMacOS ? 44 : 24}px 24px 16px`,
             textAlign: "center",
             WebkitAppRegion: "drag",
             userSelect: "none",