重构 auto-check：状态数据下沉各包，workflow 精简为纯调度

- discovery: ping 探测存活 + ARP 解析 MAC，包级 Devices map，串行扫描
- stress: 脚本生成模式（BuildScript/ParseResults），ToolSet 工具检测，包级 Results map
- report: 包级 Printed map，SaveAndPrintDeviceReport 保存+打印
- sshclient: 包级 RunCommand
- workflow: 仅持有 config，Start() 固定循环，直接调用各包方法
- config: 移除 ScanConfig.Concurrency（串行扫描无需并发数）

auto-check/pkg/discovery/arp.go

@@ -0,0 +1,77 @@
+package discovery
+
+import (
+	"os"
+	"os/exec"
+	"runtime"
+	"strings"
+)
+
+// lookupMAC 从 ARP 表获取 IP 对应的 MAC 地址（跨平台）
+// 返回空字符串表示无法获取
+func lookupMAC(ip string) string {
+	switch runtime.GOOS {
+	case "linux":
+		return macFromProcNetArp(ip)
+	case "windows":
+		return macFromWindowsArp(ip)
+	default:
+		return macFromUnixArp(ip)
+	}
+}
+
+// macFromProcNetArp 解析 Linux /proc/net/arp
+func macFromProcNetArp(ip string) string {
+	data, err := os.ReadFile("/proc/net/arp")
+	if err != nil {
+		return ""
+	}
+	for _, line := range strings.Split(string(data), "\n")[1:] {
+		fields := strings.Fields(line)
+		if len(fields) >= 4 && fields[0] == ip {
+			mac := fields[3]
+			if mac != "" && mac != "00:00:00:00:00:00" {
+				return mac
+			}
+		}
+	}
+	return ""
+}
+
+// macFromWindowsArp 解析 Windows `arp -a` 输出
+func macFromWindowsArp(ip string) string {
+	out, err := exec.Command("arp", "-a").Output()
+	if err != nil {
+		return ""
+	}
+	for _, line := range strings.Split(string(out), "\n") {
+		fields := strings.Fields(line)
+		if len(fields) >= 2 && fields[0] == ip {
+			mac := strings.ReplaceAll(fields[1], "-", ":")
+			if mac != "" && mac != "00:00:00:00:00:00" {
+				return strings.ToLower(mac)
+			}
+		}
+	}
+	return ""
+}
+
+// macFromUnixArp 解析 macOS/Linux `arp -n` 输出
+func macFromUnixArp(ip string) string {
+	out, err := exec.Command("arp", "-n", ip).Output()
+	if err != nil {
+		return ""
+	}
+	for _, line := range strings.Split(string(out), "\n") {
+		fields := strings.Fields(line)
+		for i, f := range fields {
+			if f == "("+ip+")" && i+2 < len(fields) {
+				mac := fields[i+2]
+				if mac != "" && mac != "ff:ff:ff:ff:ff:ff" {
+					return strings.ToLower(mac)
+				}
+			}
+		}
+	}
+	return ""
+}