SEP: Finalize MIME type

[idosal]

Currently, the proposal sets the MIME type to text/html+mcp, which may be easy on the eye, but doesn't meet the formal specification. This will become an issue if MCP Apps wants to register its type.

@darrelmiller proposed text/html;profile=mcp (or any other profile). It's a good option to maintain familiarity while being compliant with the spec.

[glen-84]

Perhaps it should better describe the content, like:

• profile=mcp-app
• profile=mcp-component
• profile=mcp-template

... or similar.

[idosal]

@glen-84 Makes sense. profile=mcp-app sounds good to me.

[antonpk1]

Fixed in #75.

Changed MIME type from text/html+mcp to text/html;profile=mcp-app across the specification and examples.