style: 新增窗口圆角变量并调整布局样式，修复阅读模式窗口阴影问题

1. 全局样式新增--radius-window圆角变量
2. 主布局和阅读页面添加对应圆角样式并隐藏溢出内容
3. 进入和退出阅读模式时恢复窗口阴影配置
4. 为阅读段落添加首行全角空格缩进

src/assets/global.css

@@ -25,6 +25,7 @@
   /* 圆角 */
   --radius-card: 16px;
   --radius-sm: 10px;
+  --radius-window: 12px;
 
   /* 尺寸 */
   --titlebar-height: 38px;

src/layout/MainLayout.vue

@@ -15,8 +15,18 @@
 <script setup lang="ts">
 import WindowsTitleBar from "@/layout/components/WindowsTitleBar.vue"
 import MacTitleBar from "@/layout/components/MacTitleBar.vue"
+import { getCurrentWindow } from "@tauri-apps/api/window"
+import { useSettingStore } from "@/stores/setting"
 
 const isMacos = navigator.userAgent.includes("Mac OS X")
+
+const appWindow = getCurrentWindow()
+const settingStore = useSettingStore()
+
+onMounted(() => {
+  // 从阅读模式返回时，恢复主窗口的阴影设置（避免停留在阅读器的阴影状态）
+  appWindow.setShadow(settingStore.appearance.showShadow)
+})
 </script>
 
 <style lang="scss" scoped>
@@ -25,6 +35,8 @@ const isMacos = navigator.userAgent.includes("Mac OS X")
   height: 100vh;
   background: var(--color-window-bg);
   backdrop-filter: blur(20px);
+  border-radius: var(--radius-window);
+  overflow: hidden;
   // border: 1px solid var(--color-border);
 
   :deep(.n-layout) {

src/views/Reader.vue

@@ -100,8 +100,10 @@ const paginate = () => {
       logicalLines.push("")
       continue
     }
-    for (let i = 0; i < para.length; i += charsPerLine) {
+    // 段落首行缩进两格（使用全角空格）
-      logicalLines.push(para.slice(i, i + charsPerLine))
+    const indented = "　　" + para
+    for (let i = 0; i < indented.length; i += charsPerLine) {
+      logicalLines.push(indented.slice(i, i + charsPerLine))
     }
   }
 
@@ -201,6 +203,8 @@ onMounted(() => {
 onUnmounted(() => {
   window.removeEventListener("keydown", onKeydown)
   window.removeEventListener("resize", onResize)
+  // 离开阅读模式时，恢复主窗口的阴影设置
+  appWindow.setShadow(settingStore.appearance.showShadow)
 })
 </script>
 
@@ -211,6 +215,7 @@ onUnmounted(() => {
   width: 100vw;
   height: 100vh;
   background: var(--reader-background-color);
+  border-radius: var(--radius-window);
   /* border: 1px solid rgba(255, 255, 255, 0.2); */
   padding: 10px;
   color: var(--reader-font-color);