[Saadanjum0]

Fixes #3822

When the Cloudflare socket's closed promise rejects, CloudflareSocket emits error but never close. Connection only emits end on the stream's close, so client.end() on that connection never resolves. workerd can also reject closed with undefined, which then reaches reportStreamError in pg/lib/connection.js and throws on error.code.

The fix makes the rejection path in _addClosedHandler() behave like net.Socket: emit error (wrapping an undefined rejection in an Error), then emit close if that socket is still the current one. The _cfSocket === socket check is the same one the resolve path and end() already use, so close is still emitted at most once.

Testing: added a case to pg-esm-test/pg-cloudflare.test.js that rejects closed with undefined and expects an Error followed by close. It fails on master (no close within the timeout) and passes with this change. The rest of the pg-cloudflare tests pass, and eslint and prettier are clean on the touched files.