- event-pipeline: onDisconnect now carries a reason tag (ws_closed:code=N, ws_error_frame, ws_closed_before_ready, sse_error)
- useConfigStore: store lastDisconnectReason, clear on reconnect
- send guards: embed reason in Connection lost toast so we can tell which path tripped
- lifecycle: isOpenCodeProcessHealthy hits /global/health (healthy flag) with 5s timeout instead of /session with 2s, avoids false restarts under stream load