[kissofkill]

Update:
Adds a validation entry for Monster Hunter Freedom Unite (ULUS10391) to docs/multiplayer-validation.md: the relay log signature and WebSocket behavior before the listener fix, and a two-client test with 990e875 where the quest starts and connects. The transport change originally in this PR is superseded by 990e875, so only the docs change remains.

Old:
Fixes #4

Some games (MHFU, ULUS10391) close their listening socket after accepting a connection. Accepted connections are multiplexed over the single /tcp-listen WebSocket, so closing the listener also tore down the already-accepted connection, and the relay then logged "Broken pipe" on the guest's /tcp-connect socket.

This change keeps the listener's WebSocket open after the game closes it, as long as accepted connections remain. It accepts no new connections, drops only the not-yet-accepted ones, and closes the WebSocket when the last accepted child closes. Control socket teardown and disconnect() still close everything.

Tested manually with one pair of players on MHFU (Firefox 158, self-hosted relay): a quest started and ran after the change.

[kissofkill]

The latest update (990e875) added a fix for the same bug this PR was addressing (keeping accepted streams alive when the listener closes), so I've removed my transport change and updated this PR to contain only a docs addition.

It adds the MHFU (ULUS10391) test results to docs/multiplayer-validation.md: the failure I saw before the fix, and a two-client test with 990e875 where the quest starts and the clients connect with no noticeable lag.

Thanks for the quick fix!