This PR introduces a new HTTPEvent interface as a subtype of H3Event:

interface HTTPEvent { req: ServerRequest }

_{(the real implementation supports generics and full type inference with auto-completion)}

With this simplified interface, many built-in H3 utilities (e.g., setCookie, readValidatedBody) can be used outside of H3 usage:

import { getCookie } from "h3";

export default {
  fetch(req: Request) {
    return Response.json({
      cookie: getCookie({ req }, "test") || null,
    });
  },
};

To allow accessing unified context, a new getEventContext(event) utility exposed:

• Uses H3Event.context if exists
• Uses ServerRequest.context or initializes a new (shared) one to use