Generic WebSocket consumer for the Exosphere.ATProto firehose using WebSockex.

This module connects to a relay's com.atproto.sync.subscribeRepos endpoint, decodes frames into structured messages, and dispatches those messages via an :on_event callback.

See the Firehose guide for a full walkthrough — message types, record extraction, verification, cursors, and production tips.

The :on_event callback receives (message, state) and must return an updated state. It must not raise — the consumer does not catch exceptions from the callback. If your callback can fail, wrap the failing work in a Task (or your own supervised process) and return the original state.

The consumer reconnects automatically on disconnect or connection error. A reconnect re-subscribes at the cursor the consumer has tracked in state (the seq of the last message dispatched), so it resumes where the stream left off rather than replaying from the original starting cursor. Reconnect attempts are spaced out with linear backoff plus jitter, capped at a few seconds. The tracked cursor is in-memory only — to resume a stream after a restart, persist msg.seq from your callback and pass it back via the :cursor option on next start.