Fix code review issues: import path and validation assertion

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

Author: Copilot

packages/spec/src/data/field-name-validation.test.ts

@@ -1,5 +1,5 @@
 import { describe, it, expect } from 'vitest';
-import { FieldSchema } from './src/data/field.zod';
+import { FieldSchema } from './field.zod';
 
 describe('FieldSchema name validation', () => {
   it('should reject camelCase name when provided', () => {

packages/spec/src/stack.test.ts

@@ -427,8 +427,9 @@ describe('defineStack', () => {
   it('should validate config in default mode (strict by default)', () => {
     const config = { manifest: baseManifest, objects: [] };
     const result = defineStack(config);
-    // Default is now strict=true, so result is validated and might be a different object reference
-    expect(result).toEqual(config);
+    // Default is now strict=true, so result is validated and is a different object reference
+    expect(result).not.toBe(config);  // Validation creates new object
+    expect(result).toEqual(config);   // But content is the same
     expect(result.manifest).toBeDefined();
   });