A 24-hour forced disconnect or a network blip permanently killed the
feed: next_event returned Ok(None)/Err and the stream was dead. The
struct now retains the subscribed symbols, an open() helper rebuilds the
socket, and reconnect() retries with exponential backoff (1s..30s, up to
MAX_RECONNECT_ATTEMPTS). next_event transparently reconnects on a
protocol error, a server close or a read stall, and only reports Ok(None)
after the caller has closed the stream. close() now takes &mut self.
kingchenc
0910ee6d37