Connection State Recovery: Client->Server resync

Is your feature request related to a problem? Please describe.
Connection state recovery only recovers packets that are buffered on the server. On reconnect, these are then sent to the client. But client->server packets are not handled this way.

Describe the solution you'd like
I'd like to have connection state recovery support packet retry from client to server as well. All client->server events would include an offset. On reconnect the server would send the latest client->server offset to the client and the client would repeat any missing events.

It would be nice to send the client->server offset back to the client periodically, or perhaps on every server->client event. This way the client could quickly purge events from its buffer.

This would probably involve a change to the wire format.

Describe alternatives you've considered
Practically, we end up writing a lot of extra handlers on reconnect to resync client state back to the server.

The issue names no files, tests, or entry points. Start by tracing the existing connection state recovery and reconnect flows on both client and server, then inspect the wire format; done means missing client-to-server events can be retried after reconnect and acknowledged offsets let the client purge buffered events.