`assignSocket` method is not implemented

Initially opened at https://github.com/h3js/srvx/issues/201.

`assignSocket()` is not implemented in workerd. That would allow using frameworks like express through srvx.

Bug can be reproduced with https://github.com/florian-lefebvre/srvx-cloudflare-socket-repro: when running `pnpm dev`, visiting the dev server throws this error: `The assignSocket method is not implemented`.

`assignSocket()` is being used here: https://github.com/h3js/srvx/blob/e50148058c4c89edd7cf2e7e28f597e12bfcf2c3/src/adapters/_node/web/response.ts#L10.

Closest issue I found was #2129 but didn't seem to address this problem exactly.

Logs:

```
[vite] Internal server error: The assignSocket method is not implemented
at WebServerResponse.assignSocket (node-internal:internal_http_server:407:15)
at new WebServerResponse (/home/foo/cloudflare-express/node_modules/.vite/deps_ssr/srvx_node.js?v=95586aca:910:8)
at fetchNodeHandler (/home/foo/cloudflare-express/node_modules/.vite/deps_ssr/srvx_node.js?v=95586aca:960:18)
at Object.app (converted to Web handler) [as fetch] (/home/foo/cloudflare-express/node_modules/.vite/deps_ssr/srvx_node.js?v=95586aca:999:10)
at null. (workers/runner-worker/index.js:380:20)
at maybeCaptureError (workers/runner-worker/index.js:50:10) (x2)
```