feat: add n8n_generate_workflow tool for hosted workflow generation

Add new MCP tool that enables AI-powered workflow generation from natural
language descriptions. Uses handler delegation pattern — hosting environments
inject a GenerateWorkflowHandler via EngineOptions, self-hosted instances
receive a hosted-only informational response.

Handler flows through N8NMCPEngine → SingleSessionHTTPServer →
N8NDocumentationMCPServer with helpers for createWorkflow, validateWorkflow,
autofixWorkflow, and getWorkflow.

Includes full tool documentation, tests, and corrected tools overview count.

Conceived by Romuald Członkowski - https://www.aiadvisors.pl/en

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

dist/mcp-engine.d.ts

@@ -1,6 +1,7 @@
 import { Request, Response } from 'express';
 import { InstanceContext } from './types/instance-context';
 import { SessionState } from './types/session-state';
+import { GenerateWorkflowHandler } from './types/generate-workflow';
 export interface EngineHealth {
     status: 'healthy' | 'unhealthy';
     uptime: number;
@@ -15,6 +16,7 @@ export interface EngineHealth {
 export interface EngineOptions {
     sessionTimeout?: number;
     logLevel?: 'error' | 'warn' | 'info' | 'debug';
+    generateWorkflowHandler?: GenerateWorkflowHandler;
 }
 export declare class N8NMCPEngine {
     private server;