🐛 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/connectionRpcConfig.test.ts

@@ -110,6 +110,31 @@ describe('buildRpcConnectionConfig', () => {
     expect(result.connectionParams).toBe('protocol=mysql');
   });
 
+  it('rejects unsupported OceanBase native protocol instead of falling back to MySQL', () => {
+    expect(() => buildRpcConnectionConfig({
+      id: 'conn-oceanbase-native',
+      type: 'oceanbase',
+      host: 'ob.local',
+      port: 2881,
+      user: 'root@test',
+      database: 'app',
+      connectionParams: 'protocol=native',
+    } as any)).toThrow(/不支持.*native/);
+  });
+
+  it('rejects unsupported OceanBase protocol even when form protocol is explicit MySQL', () => {
+    expect(() => buildRpcConnectionConfig({
+      id: 'conn-oceanbase-native-masked',
+      type: 'oceanbase',
+      host: 'ob.local',
+      port: 2881,
+      user: 'root@test',
+      database: 'app',
+      oceanBaseProtocol: 'mysql',
+      connectionParams: 'protocol=native',
+    } as any)).toThrow(/不支持.*native/);
+  });
+
   it('preserves extra connection params for RPC calls', () => {
     const result = buildRpcConnectionConfig({
       id: 'conn-mysql',