fix: resolve TypeScript linting errors in Phase 3 test files

- Fixed tags format from object array to string array in all test files
- Added type assertions for response.data in get-workflow-details.test.ts
- Added non-null assertions for workflow.nodes in get-workflow.test.ts
- All TypeScript linting errors now resolved

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

tests/integration/n8n-api/workflows/get-workflow-structure.test.ts

@@ -46,7 +46,7 @@ describe('Integration: handleGetWorkflowStructure', () => {
       const workflow = {
         ...SIMPLE_WEBHOOK_WORKFLOW,
         name: createTestWorkflowName('Get Structure - Simple'),
-        tags: [{ name: 'mcp-integration-test' }]
+        tags: ['mcp-integration-test']
       };
 
       const created = await client.createWorkflow(workflow);
@@ -92,7 +92,7 @@ describe('Integration: handleGetWorkflowStructure', () => {
       const workflow = {
         ...MULTI_NODE_WORKFLOW,
         name: createTestWorkflowName('Get Structure - Complex'),
-        tags: [{ name: 'mcp-integration-test' }]
+        tags: ['mcp-integration-test']
       };
 
       const created = await client.createWorkflow(workflow);