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/http-server-single-session.d.ts

@@ -2,6 +2,10 @@
 import express from 'express';
 import { InstanceContext } from './types/instance-context';
 import { SessionState } from './types/session-state';
+import { GenerateWorkflowHandler } from './types/generate-workflow';
+export interface SingleSessionHTTPServerOptions {
+    generateWorkflowHandler?: GenerateWorkflowHandler;
+}
 export declare class SingleSessionHTTPServer {
     private transports;
     private servers;
@@ -14,7 +18,8 @@ export declare class SingleSessionHTTPServer {
     private sessionTimeout;
     private authToken;
     private cleanupTimer;
-    constructor();
+    private generateWorkflowHandler?;
+    constructor(options?: SingleSessionHTTPServerOptions);
     private startSessionCleanup;
     private cleanupExpiredSessions;
     private removeSession;