Live visualizer

[frankmcsherry]

Not certain it should merge here, vs be a new crate maybe, but a Claude-assisted live visualizer for timely dataflows. You start a server and the register the worker to register a logger.

  let server = Server::start(51371);

  // inside execute closure:
  server.register(worker);

There's an example, and it all seems to work. :D

[frankmcsherry]

The Rust code for the visualizer is .. not great. It serializes all events to JSON under a mutex and then stores them in an MPSC until a client connects. This may want to be a DD project, to make sure that we have access to efficient aggregation and state roll-up.