Change from text/vnd.mcp.ui+html to text/html+mcp.
Rationale:
- It's an unregistered subtype, allowed for private use
- The +suffix form indicates MCP-specific semantics (postMessage protocol)
- Content is still valid HTML and can be rendered as-such
- Following RFC 6838, +mcp could be registered as an official suffix
🤖 Generated with [Claude Code](https://claude.com/claude-code)
Co-Authored-By: Claude <noreply@anthropic.com>