SEP-1865 MCP Apps Extension sample implementation

SEP-1865 MCP Apps Extension, even though in draft currently, will change how AI agents deliver interactive experiences.

The idea: MCP tools return HTML/CSS/JS directly. The client renders it in a sandboxed iframe. That's it.

Your AI agent calls a tool, gets back a full interactive UI. Dashboard, form, chart - whatever you need.

How it works: - Tool returns text/html+mcp resource - Client renders in iframe with CSP - UI talks back via JSON-RPC 2.0 postMessage - Fully sandboxed, secure by default

Built a sample implementation with vanilla Web Components. This is where MCP is heading.