When sway's event-subscription send buffer overflows during an event
flood, sway closes the client connection. The sway IPC event worker
(SleeperThread running handleEvent -> recv) then threw on every
iteration and the SleeperThread immediately re-invoked it, leaving the
sway modules broken while busy-looping on a dead socket and pegging a
CPU.
Mirror the niri backend's reconnect loop: on a read/EOF/parse error from
the event socket, close the old connection, back off for a couple of
seconds (so we don't busy-spin), re-open the socket and replay the same
subscriptions, then resume. A running_ flag set at the start of teardown
makes the worker bail out cleanly instead of reconnecting to a socket
that is being closed on purpose. The IPC message protocol and event
parsing are unchanged.
Fixes#3166.