docs: MCP SDKs link in host-integration.md returns 404 #3589

Description

In docs/host-integration.md, the "Additional Resources" section links to the Java MCP SDK overview, which now returns 404 after the modelcontextprotocol.io docs restructure:

• File: docs/host-integration.md (line 184)
• Current link text/URL: [MCP SDKs](https://modelcontextprotocol.io/sdk/java/mcp-overview)
• curl -sI https://modelcontextprotocol.io/sdk/java/mcp-overview → 404

The SDK overview is now served under the versioned docs path. https://modelcontextprotocol.io/docs/sdk returns 200 and renders the "SDKs" page.

Suggested fix

Point the entry at https://modelcontextprotocol.io/docs/sdk:

-- [MCP SDKs](https://modelcontextprotocol.io/sdk/java/mcp-overview)
+- [MCP SDKs](https://modelcontextprotocol.io/docs/sdk)

Scope

This is the only occurrence of the old URL in the repository. I'll open a PR with this one-line change; other links in the same guide are unaffected by this fix.