A relay-side close the transport never surfaces (observed as a CLOSE_WAIT
socket behind Cloudflare, #98097) parks the read loop forever while the
gateway keeps reporting connected: inbound stops, gateway_state.json stays
healthy, and only a restart recovers. The library keepalive should catch
this first, but as a last resort the read side now waits at most
_WS_READ_IDLE_TIMEOUT (300s) for a frame before raising into the existing
reconnect path, which re-authenticates and re-subscribes with per-channel
since filters intact.
Fixes#98097
liuhao1024
94d86fa4de