Add best exit selection (#486)

* docs: add best exit selection design

* feat: add best exit selection

vite-frontend/src/pages/tunnel.tsx

@@ -91,7 +91,7 @@ import {
 interface ChainTunnel {
   nodeId: number;
   protocol?: string; // 'tls' | 'wss' | 'tcp' | 'mtls' | 'mwss' | 'mtcp' | 'kcp' - 转发链协议
-  strategy?: string; // 'fifo' | 'round' | 'rand' - 仅转发链需要
+  strategy?: string; // 'fifo' | 'round' | 'rand' | 'best' - 仅转发链/多出口需要
   chainType?: number; // 1: 入口, 2: 转发链, 3: 出口
   inx?: number; // 转发链序号
   connectIp?: string; // 连接IP（多IP节点指定连接地址）
@@ -2901,6 +2901,7 @@ export default function TunnelPage() {
                                 <SelectItem key="fifo">主备</SelectItem>
                                 <SelectItem key="round">轮询</SelectItem>
                                 <SelectItem key="rand">随机</SelectItem>
+                                <SelectItem key="best">最优</SelectItem>
                               </Select>
                             </div>