Add Introduction heading and gateway framing to vMCP index

Author: danbarr

docs/toolhive/guides-vmcp/index.mdx

@@ -3,9 +3,12 @@ title: Virtual MCP Server
 description: Aggregate multiple MCP servers into a single unified endpoint.
 ---
 
-Virtual MCP Server (vMCP) is a feature of the ToolHive Kubernetes Operator that
-aggregates multiple backend MCP servers into a single endpoint, enabling unified
-tool access, centralized authentication, and multi-step workflows.
+## Introduction
+
+Virtual MCP Server (vMCP) is ToolHive's MCP gateway. It aggregates multiple
+backend MCP servers into a single endpoint, giving clients unified tool access,
+centralized authentication, and multi-step workflows — all through one
+connection.
 
 ## Where to start