feat(queue): 自 go-hua/queue 原样迁入链式队列

- 代码与测试不变，附 examples/queue 例程与包 README(含哨兵头结点 Pop 语义说明)

queue/queue_test.go

@@ -0,0 +1,44 @@
+package queue
+
+import "testing"
+
+func TestCreateAndLength(t *testing.T) {
+	q := &QueueNode{}
+	q.Create(1, 2, 3)
+	if got := q.Length(); got != 3 {
+		t.Errorf("Length = %d, want 3", got)
+	}
+}
+
+func TestPush(t *testing.T) {
+	q := &QueueNode{}
+	q.Create("a")
+	q.Push("b")
+	if got := q.Length(); got != 2 {
+		t.Errorf("Push 后 Length = %d, want 2", got)
+	}
+}
+
+func TestPop(t *testing.T) {
+	q := &QueueNode{}
+	q.Create(1, 2, 3)
+	// Pop 在头结点（哨兵）上调用，跳过第一个元素并返回头结点 Data
+	q.Pop()
+	if got := q.Length(); got != 2 {
+		t.Errorf("Pop 后 Length = %d, want 2", got)
+	}
+}
+
+func TestCreateEmpty(t *testing.T) {
+	q := &QueueNode{}
+	q.Create() // 无元素，不应 panic
+	if got := q.Length(); got != 0 {
+		t.Errorf("空 Create 后 Length = %d, want 0", got)
+	}
+}
+
+func TestPrint(t *testing.T) {
+	q := &QueueNode{}
+	q.Create(1, 2, 3)
+	q.Print() // 仅验证不 panic
+}