style(docs): adjust sidebar spacing and typography for better readability

Improve sidebar navigation spacing and line heights to enhance visual hierarchy and readability. Move CSS from external file to inline style in config for better maintainability.

docs/.vitepress/config.mjs

@@ -6,7 +6,54 @@ export default defineConfig({
   description: 'Easy-Vibe 中文实战课 - 零基础学会用 AI 干实际工作',
   head: [
     ['link', { rel: 'icon', href: '/logo.png' }],
-    ['link', { rel: 'stylesheet', href: '/style.css' }]
+    [
+      'style',
+      {},
+      `
+        :root {
+          --vp-sidebar-nav-section-gap: 8px;
+        }
+        .VPSidebarItem.level-0 {
+          padding-bottom: 4px !important;
+        }
+        .VPSidebarItem.level-0 > .item {
+          padding-bottom: 2px !important;
+        }
+        .VPSidebarItem.level-1 .item,
+        .VPSidebarItem.level-2 .item,
+        .VPSidebarItem.level-3 .item,
+        .VPSidebarItem.level-4 .item {
+          padding-top: 2px !important;
+          padding-bottom: 2px !important;
+          min-height: 24px !important;
+        }
+        .VPSidebarGroup {
+          padding-top: 6px !important;
+          padding-bottom: 6px !important;
+        }
+        .VPSidebarItem.level-0 + .VPSidebarItem.level-1 {
+          margin-top: -2px !important;
+        }
+        .VPSidebarItem.level-0 .text {
+          line-height: 1.3 !important;
+        }
+        .VPSidebarItem.level-1 .text,
+        .VPSidebarItem.level-2 .text,
+        .VPSidebarItem.level-3 .text {
+          line-height: 1.4 !important;
+          padding: 0 !important;
+        }
+        .VPSidebarItem .VPLink {
+          padding-top: 2px !important;
+          padding-bottom: 2px !important;
+          min-height: auto !important;
+        }
+        .VPSidebarItem .item {
+          padding-top: 2px !important;
+          padding-bottom: 2px !important;
+        }
+      `
+    ]
   ],
   themeConfig: {
     logo: '/logo.png',