Add Arch mirror manager: benchmark, apply, pin, restore, status

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01QKxGW1raAWaqeU8WdHsMsp

cn/mirrors.json

@@ -0,0 +1,12 @@
+{
+  "mirrors": [
+    { "id": "tuna", "name": "清华大学 TUNA", "region": "cn", "url": "https://mirrors.tuna.tsinghua.edu.cn/archlinux" },
+    { "id": "ustc", "name": "中国科学技术大学", "region": "cn", "url": "https://mirrors.ustc.edu.cn/archlinux" },
+    { "id": "aliyun", "name": "阿里云", "region": "cn", "url": "https://mirrors.aliyun.com/archlinux" },
+    { "id": "tencent", "name": "腾讯云", "region": "cn", "url": "https://mirrors.cloud.tencent.com/archlinux" },
+    { "id": "netease", "name": "网易", "region": "cn", "url": "https://mirrors.163.com/archlinux" },
+    { "id": "sjtu", "name": "上海交通大学", "region": "cn", "url": "https://mirror.sjtu.edu.cn/archlinux" },
+    { "id": "geo", "name": "Arch 官方 Geo Mirror", "region": "global", "url": "https://geo.mirror.pkgbuild.com" },
+    { "id": "worldwide", "name": "Arch 官方 Worldwide", "region": "global", "url": "https://mirror.rackspace.com/archlinux" }
+  ]
+}