refactor(workflows): remove unused import and fix type assertion

Clean up code by removing unused isWorkflowTemplate import and replacing any type assertion with proper typing for step.engine

Author: moazbuilds

src/workflows/execution/workflow.ts

@@ -155,7 +155,7 @@ export async function runWorkflow(options: RunWorkflowOptions = {}): Promise<voi
     // Ensure the selected engine is used during execution
     // (executeStep falls back to default engine if step.engine is unset)
     // Mutate current step to carry the chosen engine forward
-    (step as any).engine = engineType;
+    step.engine = engineType;
 
     // Resolve model and reasoning effort for display
     const engineModule = registry.get(engineType);

src/workflows/templates/loader.ts

@@ -3,7 +3,7 @@ import { existsSync } from 'node:fs';
 import { createRequire } from 'node:module';
 import { fileURLToPath, pathToFileURL } from 'node:url';
 import type { WorkflowTemplate } from './types.js';
-import { isWorkflowTemplate, validateWorkflowTemplate } from './validator.js';
+import { validateWorkflowTemplate } from './validator.js';
 import { ensureTemplateGlobals } from './globals.js';
 
 // Package root resolution