Revert "fix: handle the client disconnect so that the server does not crash."

[cliffhall]

Reverts #380

I realized the problem is already be fixed in the #428, and there's no need to have to refactor that one to remove most of this one's changes.

[cliffhall]

@olaservo I merged #380 after having previously fully testing it and including videos of the problem and the fix working locally.

But then I realized that I had jumped the gun. This PR works with the backingServerTransport which is refactored out of existence in #428 when adding support for multiple instances of the client to connect to the same server. Part of that effort was doing away with the single backingServerTransport and having a separate server transport for every web app transport. And that PR handles closing of the client properly, cleaning up both transports.

Here is a video of connecting to an STDIO server with that code, and the server is never crashed by a disconnecting client.

Screen.Recording.2025-05-28.at.1.02.11.PM.mov