feat(types): add resolveI18nLabel protocol utility and I18nLabel type re-export

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

Author: Copilot

ROADMAP.md

@@ -1251,4 +1251,12 @@ ObjectQL implements the **data layer compiler** portion of the ObjectStack proto
 
 ---
 
+## Cross-Repo Notes
+
+| Target Repo | Issue | Description |
+|---|---|---|
+| `objectstack-ai/objectui` | `@object-ui/plugin-designer` build failure | Published `@object-ui/react@3.0.3` is missing `resolveI18nLabel` export (source has it, npm dist does not). Either republish `@object-ui/react` or update `plugin-designer` to import `resolveI18nLabel` from `@objectql/types` which now exports it ([PR #411](https://github.com/objectstack-ai/objectql/pull/411)). |
+
+---
+
 > **Historical Reference:** The core refactoring design document is archived at `docs/DESIGN_CORE_REFACTOR.md` (Status: ✅ Completed — [PR #373](https://github.com/objectstack-ai/objectql/pull/373)).

packages/foundation/types/src/util.ts

@@ -10,6 +10,34 @@
  */
 
 import { ObjectConfig, FieldConfig, FieldType, IntrospectedSchema } from './index';
+import { UI } from '@objectstack/spec';
+import { z } from 'zod';
+
+/**
+ * Re-export I18nLabel protocol type from @objectstack/spec.
+ * 
+ * I18nLabel is a union of plain string or structured i18n object { key, defaultValue?, params? }.
+ * Used across the ecosystem for internationalized labels.
+ */
+export type I18nLabel = z.infer<typeof UI.I18nLabelSchema>;
+
+/**
+ * Resolves an I18nLabel to a plain string.
+ *
+ * I18nLabel can be either a string or an object { key, defaultValue?, params? }.
+ * When it's an object, returns the defaultValue or the key as fallback.
+ * When it's undefined or null, returns undefined.
+ *
+ * @param label - The I18nLabel value to resolve
+ * @returns The resolved plain string, or undefined if the input is nullish
+ */
+export function resolveI18nLabel(
+    label: string | { key: string; defaultValue?: string; params?: Record<string, unknown> } | undefined | null
+): string | undefined {
+    if (label === undefined || label === null) return undefined;
+    if (typeof label === 'string') return label;
+    return label.defaultValue || label.key;
+}
 
 export function toTitleCase(str: string): string {
     return str

packages/foundation/types/test/util.test.ts

@@ -0,0 +1,55 @@
+/**
+ * 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.
+ */
+
+import { resolveI18nLabel } from '../src/util';
+
+describe('resolveI18nLabel', () => {
+    it('should return undefined for undefined input', () => {
+        expect(resolveI18nLabel(undefined)).toBeUndefined();
+    });
+
+    it('should return undefined for null input', () => {
+        expect(resolveI18nLabel(null)).toBeUndefined();
+    });
+
+    it('should return the string as-is for plain string input', () => {
+        expect(resolveI18nLabel('Hello')).toBe('Hello');
+    });
+
+    it('should return empty string for empty string input', () => {
+        expect(resolveI18nLabel('')).toBe('');
+    });
+
+    it('should return defaultValue from i18n object when available', () => {
+        expect(resolveI18nLabel({
+            key: 'views.task_list.label',
+            defaultValue: 'Task List',
+        })).toBe('Task List');
+    });
+
+    it('should return key as fallback when defaultValue is not provided', () => {
+        expect(resolveI18nLabel({
+            key: 'views.task_list.label',
+        })).toBe('views.task_list.label');
+    });
+
+    it('should return key as fallback when defaultValue is empty string', () => {
+        expect(resolveI18nLabel({
+            key: 'views.task_list.label',
+            defaultValue: '',
+        })).toBe('views.task_list.label');
+    });
+
+    it('should handle i18n object with params', () => {
+        expect(resolveI18nLabel({
+            key: 'items.count',
+            defaultValue: '{count} items',
+            params: { count: 5 },
+        })).toBe('{count} items');
+    });
+});