agent-singbox: 优先从 GitHub Release 下载预编译二进制，失败再源码编译

scripts/agent-singbox.sh

@@ -14,6 +14,41 @@ if [[ -x "$target" && -x "$stats_target" && "${2:-}" != '--force' ]]; then
   exit 0
 fi
 
+# 优先从 GitHub Release 下载预编译二进制，免去现场编译
+# Release tag: sing-box-v1.13.21，需上传 nexusgate-sing-box-linux-<arch> 和 nexusgate-sing-box-stats-linux-<arch>
+try_prebuilt() {
+  local arch dl_arch release_tag base_url tmp_bin tmp_stats
+  case "$(uname -m)" in
+    x86_64|amd64) dl_arch=amd64 ;;
+    aarch64|arm64) dl_arch=arm64 ;;
+    *) return 1 ;;
+  esac
+  release_tag="${NG_SINGBOX_RELEASE:-sing-box-v1.13.21}"
+  base_url="https://github.com/imamoxilin/NexusGate/releases/download/${release_tag}"
+  tmp_bin="$(mktemp /tmp/nexusgate-singbox-bin.XXXXXX)"
+  tmp_stats="$(mktemp /tmp/nexusgate-singbox-stats.XXXXXX)"
+  trap 'rm -f -- "$tmp_bin" "$tmp_stats"' RETURN
+  printf '尝试从 GitHub Release 下载预编译 sing-box...\n'
+  if curl -fL --retry 2 --connect-timeout 15 -o "$tmp_bin" "${base_url}/nexusgate-sing-box-linux-${dl_arch}" 2>/dev/null && \
+     curl -fL --retry 2 --connect-timeout 15 -o "$tmp_stats" "${base_url}/nexusgate-sing-box-stats-linux-${dl_arch}" 2>/dev/null; then
+    chmod +x "$tmp_bin" "$tmp_stats"
+    # 简单验证二进制可执行
+    if "$tmp_bin" version >/dev/null 2>&1; then
+      install -m 0755 "$tmp_bin" "${target}.next"
+      install -m 0755 "$tmp_stats" "${stats_target}.next"
+      mv -f "${target}.next" "$target"
+      mv -f "${stats_target}.next" "$stats_target"
+      printf 'sing-box 预编译版安装完成：%s\n' "$target"
+      return 0
+    fi
+  fi
+  printf '预编译包下载失败，回退到源码编译\n'
+  return 1
+}
+if [[ "${NG_SINGBOX_NO_PREBUILT:-}" != "1" ]]; then
+  try_prebuilt && exit 0
+fi
+
 build_dir="$(mktemp -d /tmp/nexusgate-singbox.XXXXXX)"
 trap 'rm -rf -- "$build_dir"' EXIT
 # Go's module and build caches can occupy hundreds of MB indefinitely on a