feat(driver): add DriverTypeOpenGauss constant for openGauss data source

sqle/driver/v2/util.go

@@ -36,6 +36,7 @@ const (
 	DriverTypeTBase          = "TBase"
 	DriverTypeHANA           = "HANA"
 	DriverTypeGaussDB        = "GaussDB"
+	DriverTypeOpenGauss      = "openGauss"
 )
 
 type DriverNotSupportedError struct {

sqle/driver/v2/util_test.go

@@ -0,0 +1,28 @@
+package driverV2
+
+import (
+	"testing"
+)
+
+// TestDriverTypeOpenGauss_Const_EE 断言 sqle-ee 副本中 DriverTypeOpenGauss 常量字面值
+// 严格为 "openGauss"（首字母小写 o，G 大写），并回归断言 DriverTypeGaussDB == "GaussDB"，
+// 保证两个 GaussDB / openGauss 字面值与 design §4.4 严格匹配契约一致。
+//
+// 任何对该字面值的归一化（strings.ToLower / trim / 大小写改写）都会让本测试 fail，
+// 提示 code_review 阶段同步落地的 sqle CE 副本必须保持完全一致。
+func TestDriverTypeOpenGauss_Const_EE(t *testing.T) {
+	cases := map[string]struct {
+		got  string
+		want string
+	}{
+		"openGauss literal":          {got: DriverTypeOpenGauss, want: "openGauss"},
+		"GaussDB literal regression": {got: DriverTypeGaussDB, want: "GaussDB"},
+	}
+	for name, tc := range cases {
+		t.Run(name, func(t *testing.T) {
+			if tc.got != tc.want {
+				t.Fatalf("constant literal drift: got %q, want %q", tc.got, tc.want)
+			}
+		})
+	}
+}