With TRACES_ENABLED off, LLM calls record no GenAI metrics, and a streamed
answer is joined into a preview only when a span keeps it. Agent runs and
continuations build their invoke_agent span in one place, which now reads
the model from model_id. The trace panel shows a stream's model time next
to how long it was open. Adds missing type hints.
The dispatcher and each retriever's search open retrieval spans recording
sources, chunk counts, top scores and a chunk preview. The shared query
embedding, every per-source vector search and the prescreen rerank get
their own spans; pool workers carry the trace so they nest correctly.
arc53-machine