Server fetch ignore init if first param is a Request

Describe the bug

normalize_fetch_input ignores init if info is a Request:

/**
 * @param {RequestInfo | URL} info
 * @param {RequestInit | undefined} init
 * @param {URL} url
 */
function normalize_fetch_input(info, init, url) {
	if (info instanceof Request) {
		return info;
	}

	return new Request(typeof info === 'string' ? new URL(info, url) : info, init);
}

https://github.com/sveltejs/kit/blob/main/packages/kit/src/runtime/server/fetch.js#L188

When init is ignored, the server fetch function doesn't behave like it does in the browser.

Reproduction

For example:

export const load: PageServerLoad = async ({ fetch }) => {
  const req = new Request(someUrl);
  const init = { headers: { 'Authorization': 'some-token } };
  // this ignores init
  const response = await fetch(req, init);

  // this uses init with the headers
  const response2 = await fetch(new Request(req, init));
}

In the browser each fetch call would behave the same. mdn has a similar example - https://developer.mozilla.org/en-US/docs/Web/API/RequestInit#passing_options_into_both_request_and_fetch

Logs

System Info

npmPackages:
    @sveltejs/adapter-auto: ^6.1.0 => 6.1.1 
    @sveltejs/adapter-node: ^5.4.0 => 5.4.0 
    @sveltejs/kit: ^2.43.2 => 2.50.0 
    @sveltejs/vite-plugin-svelte: ^6.2.1 => 6.2.1 
    svelte: ^5.39.5 => 5.39.10 
    vite: 7.1.11 => 7.1.11

Severity

annoyance

Additional Information

No response

Start in packages/kit/src/runtime/server/fetch.js at normalize_fetch_input and compare its Request handling with the browser Fetch API behavior described in the issue. Reproduce the Request-plus-init case, then verify that server fetch applies the init options consistently with the equivalent new Request(req, init) example.