feat: 初始提交（仅核心代码，已排除大文件）

public/common/nav.js

@@ -0,0 +1,26 @@
+(async function(){
+  try {
+    const wrap = document.querySelector('#topbar')
+    if (!wrap) return
+    const res = await fetch('/common/nav.html')
+    const html = await res.text()
+    wrap.innerHTML = html
+    const path = location.pathname.toLowerCase()
+    let key = ''
+    if (path.includes('/tools/weibo/')) key = 'weibo'
+    else if (path.includes('/tools/markets/')) key = 'markets'
+    else if (path.includes('/tools/wall/')) key = 'wall'
+    else if (path.includes('/tools/funds/')) key = 'funds'
+    else if (path.includes('/tools/ccb_private_funds/')) key = 'ccb_private_funds'
+    else if (path.includes('/tools/cloud/')) key = 'cloud'
+    else if (path.includes('/tools/weekly/')) key = 'weekly'
+    else if (path.includes('/tools/ai-lib/')) key = 'ai-lib'
+    else if (path.includes('/tools/expense/')) key = 'expense'
+    if (key) {
+      wrap.querySelectorAll('a.tab').forEach(a => {
+        if (a.dataset.key === key) a.classList.add('active')
+        else a.classList.remove('active')
+      })
+    }
+  } catch {}
+})()