🐛 fix(tdengine): 修复查询结果仅显示执行日志

- TDengine 只读查询跳过不支持的多结果集探测
- 保证可选驱动代理通过普通查询返回完整行列数据
- 补充应用层与驱动层回归测试

Fixes #610

internal/app/methods_db.go

@@ -1700,6 +1700,11 @@ func shouldPreferPlainReadQueryResult(dbType string) bool {
 		"gaussdb", "gauss_db", "gauss-db",
 		"dameng", "dm", "dm8":
 		return true
+	case "tdengine":
+		// TDengine only implements the plain query API. The optional driver-agent
+		// exposes a transport-level multi-result method, but reports it unsupported.
+		// Skipping that probe prevents a successful SELECT from becoming an empty result.
+		return true
 	default:
 		return false
 	}