Let me reuse a HTMLTracer for multiple prompt renders

[roblourens]

Might be nice if I can have one HTMLTracer instance running a server, and reuse it for multiple render calls, so I don't need a new port per call?

Trying to get this to show up automatically in chat-extension-utils, and it seems weird to occupy all of these ports. Maybe it's fine though. The library also doesn't know when to dispose the server.