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>

src/index.ts

@@ -21,6 +21,12 @@ export {
 export type {
   SessionState
 } from './types/session-state';
+export type {
+  GenerateWorkflowArgs,
+  GenerateWorkflowResult,
+  GenerateWorkflowHandler,
+  GenerateWorkflowHelpers
+} from './types/generate-workflow';
 
 // UI module exports
 export type { UIAppConfig, UIMetadata } from './mcp/ui/types';