fix: integrate webhook autofixer with MCP server and improve template sanitization

- Register n8n_autofix_workflow handler in MCP server
- Export n8nAutofixWorkflowDoc in tool documentation indices
- Use normalizeNodeType utility in workflow validator for consistent type handling
- Add defensive null checks in template sanitizer to prevent runtime errors
- Update workflow validator test to handle new error message formats

These changes complete the webhook autofixer integration, ensuring the tool
is properly exposed through the MCP server and documentation system.

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

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

src/mcp/tool-docs/index.ts

@@ -43,6 +43,7 @@ import {
   n8nDeleteWorkflowDoc,
   n8nListWorkflowsDoc,
   n8nValidateWorkflowDoc,
+  n8nAutofixWorkflowDoc,
   n8nTriggerWebhookWorkflowDoc,
   n8nGetExecutionDoc,
   n8nListExecutionsDoc,
@@ -98,6 +99,7 @@ export const toolsDocumentation: Record<string, ToolDocumentation> = {
   n8n_delete_workflow: n8nDeleteWorkflowDoc,
   n8n_list_workflows: n8nListWorkflowsDoc,
   n8n_validate_workflow: n8nValidateWorkflowDoc,
+  n8n_autofix_workflow: n8nAutofixWorkflowDoc,
   n8n_trigger_webhook_workflow: n8nTriggerWebhookWorkflowDoc,
   n8n_get_execution: n8nGetExecutionDoc,
   n8n_list_executions: n8nListExecutionsDoc,