feat: 新增 proc.list/user.list/pkg.list 命令

proc.list 列出所有进程（ps aux/tasklist）
user.list 列出系统用户（getent passwd/net user）
pkg.list 列出已安装软件包（dpkg/rpm/apk/brew/winget）

internal/executor/userlist.go

@@ -0,0 +1,51 @@
+package executor
+
+import (
+	"context"
+	"fmt"
+	"os/exec"
+	"runtime"
+	"strings"
+)
+
+// runUserList implements `kopsc user list`: list all users.
+func runUserList(ctx context.Context, req BuiltinRequest) error {
+	switch runtime.GOOS {
+	case "linux", "darwin":
+		return userListUnix(ctx, req)
+	case "windows":
+		cmd := exec.CommandContext(ctx, "net", "user")
+		cmd.Stdout = req.Stdout
+		cmd.Stderr = req.Stderr
+		return cmd.Run()
+	default:
+		return fmt.Errorf("不支持的操作系统: %s", runtime.GOOS)
+	}
+}
+
+func userListUnix(ctx context.Context, req BuiltinRequest) error {
+	// Try getent first (more portable), fall back to reading /etc/passwd
+	if path, err := exec.LookPath("getent"); err == nil {
+		cmd := exec.CommandContext(ctx, path, "passwd")
+		cmd.Stdout = req.Stdout
+		cmd.Stderr = req.Stderr
+		return cmd.Run()
+	}
+	// Fall back to /etc/passwd
+	out, err := exec.CommandContext(ctx, "cat", "/etc/passwd").Output()
+	if err != nil {
+		return fmt.Errorf("读取用户列表失败: %w", err)
+	}
+	fmt.Fprintln(req.Stdout, "用户名:UID:GID:描述:家目录:Shell")
+	for _, line := range strings.Split(string(out), "\n") {
+		if line == "" {
+			continue
+		}
+		fields := strings.Split(line, ":")
+		if len(fields) >= 7 {
+			fmt.Fprintf(req.Stdout, "%s:%s:%s:%s:%s:%s\n",
+				fields[0], fields[2], fields[3], fields[4], fields[5], fields[6])
+		}
+	}
+	return nil
+}