Fix Jest ESM compatibility for @objectstack/core in plugin-validator

- Add mock for @objectstack/core to handle ESM import.meta usage
- Update jest.config.js to use the mock via moduleNameMapper
- Tests now pass successfully (71 tests passed)

Co-authored-by: hotlong <50353452+hotlong@users.noreply.github.com>

Author: Copilot

packages/foundation/plugin-validator/jest.config.js

@@ -12,6 +12,7 @@ module.exports = {
   testMatch: ['**/test/**/*.test.ts'],
   moduleNameMapper: {
     '^@objectql/(.*)$': '<rootDir>/../$1/src',
+    '^@objectstack/core$': '<rootDir>/test/__mocks__/@objectstack/core.ts',
   },
   transform: {
     '^.+\\.(t|j)sx?$': ['ts-jest', {

packages/foundation/plugin-validator/test/__mocks__/@objectstack/core.ts

@@ -0,0 +1,27 @@
+/**
+ * ObjectQL
+ * Copyright (c) 2026-present ObjectStack Inc.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+/**
+ * Mock for @objectstack/core to enable Jest testing
+ * 
+ * Since @objectstack/core@0.9.2 uses ES modules with import.meta,
+ * which Jest doesn't support well, we provide this mock for testing.
+ */
+
+export const createLogger = jest.fn(() => ({
+  trace: jest.fn(),
+  debug: jest.fn(),
+  info: jest.fn(),
+  warn: jest.fn(),
+  error: jest.fn(),
+  fatal: jest.fn(),
+}));
+
+export const ObjectKernel = jest.fn();
+export const LiteKernel = jest.fn();
+export const createApiRegistryPlugin = jest.fn();