fix: resolve module mocking issue in batch-processor tests

- Move MockMetadataGenerator class definition inside vi.mock factory
- Fix OpenAI mock to use class constructor pattern
- Resolves ReferenceError: Cannot access before initialization

Reduces test failures from total failure to just 2 legitimate bugs

🤖 Generated with Claude Code

Co-Authored-By: Claude <noreply@anthropic.com>

tests/unit/templates/batch-processor.test.ts

@@ -23,7 +23,13 @@ const mockClient = {
 
 vi.mock('openai', () => {
   return {
-    default: vi.fn().mockImplementation(() => mockClient)
+    default: class MockOpenAI {
+      files = mockClient.files;
+      batches = mockClient.batches;
+      constructor(config: any) {
+        // Mock constructor
+      }
+    }
   };
 });
 
@@ -33,12 +39,13 @@ const mockGenerator = {
   parseResult: vi.fn()
 };
 
-class MockMetadataGenerator {
+vi.mock('../../../src/templates/metadata-generator', () => {
+  // Define MockMetadataGenerator inside the factory to avoid hoisting issues
+  class MockMetadataGenerator {
     createBatchRequest = mockGenerator.createBatchRequest;
     parseResult = mockGenerator.parseResult;
-}
+  }
   
-vi.mock('../../../src/templates/metadata-generator', () => {
   return {
     MetadataGenerator: MockMetadataGenerator
   };