The spinner (.session-state-indicator.is-streaming) can remain spinning
indefinitely on completed sessions when the INFLIGHT in-memory cache is
not cleaned up due to abnormal stream termination (page refresh, network
disconnect, gateway restart).
Add a staleness guard in _isSessionLocallyStreaming: if the server
reports is_streaming=false and last_message_at is older than 5 minutes,
force the streaming state to false regardless of stale INFLIGHT entries.
Frank Song
c60078b356
