🐛 fix(oceanbase): 修复 OceanBase 协议模式识别与缓存隔离

- 支持 MySQL/Oracle 租户协议在前后端统一解析
- 拒绝 Native 协议并避免误回退为 MySQL
- 修复 Oracle 模式下元数据、DDL、SQL 方言识别
- 修复连接缓存键与实际协议解析优先级不一致问题
- 补充前后端协议解析与缓存隔离回归测试

frontend/src/utils/sqlDialect.ts

@@ -1,3 +1,5 @@
+import { resolveOceanBaseProtocolForDialect } from './oceanBaseProtocol';
+
 export type ColumnTypeOption = { value: string };
 
 export type SqlFunctionCompletion = {
@@ -34,9 +36,7 @@ const optionValues = (values: string[]): ColumnTypeOption[] => values.map((value
 
 const normalizeRawDialect = (value: string): string => String(value || '').trim().toLowerCase();
 
-export const normalizeOceanBaseSqlProtocol = (value: unknown): 'mysql' | 'oracle' => (
-  String(value || '').trim().toLowerCase() === 'oracle' ? 'oracle' : 'mysql'
-);
+export const normalizeOceanBaseSqlProtocol = resolveOceanBaseProtocolForDialect;
 
 export const resolveSqlDialect = (
   rawType: string,