Document STDIO on k8s limitation (#238)

Co-authored-by: Copilot <[email protected]>

Author: eleftherias

docs/toolhive/guides-k8s/run-mcp-k8s.mdx

@@ -65,9 +65,17 @@ flowchart LR
   Proxy -->|Attaches/STDIO| MCP
 ```
 
+:::info[STDIO Transport Limitation]
+
+MCP servers using STDIO transport support only a single client connection at a
+time. If you need to support multiple users or concurrent client connections,
+use SSE (Server-Sent Events) or Streamable HTTP transport instead.
+
+:::
+
 ### Streamable HTTP and SSE transport flow
 
-For MCP servers using Server-Sent Events (SSE) or Stremable HTTP transport, the
+For MCP servers using Server-Sent Events (SSE) or Streamable HTTP transport, the
 proxy creates both a pod and a headless service. This allows direct HTTP/SSE or
 HTTP/Streamable HTTP communication between the proxy and MCP server while
 maintaining network isolation and service discovery.