TracingSubscriber

Bridges a thread's durable run events to a org.llm4s.trace.Tracing: each becomes a TraceEvent.CustomEvent named graph.<event> (RunStarted is graph.run_started), stamped with the record's timestamp. Its data holds threadId, runId, seq, checkpointId, taskId and nodeId (null when absent) and the event's own fields. Live progress is not traced.

A subscription that falls behind is disconnected like any other: a StreamEvent.Disconnected(lastSeq, DisconnectReason.Lagging) ends tracing, and is only logged. Nothing re-attaches by itself: to keep tracing, the caller attaches again with afterSeq = lastSeq, which replays from the first event not traced.