Code review finding (P2): when chat_stream successfully emits the first
chunk (broadcasted to UI) but then breaks during subsequent chunks, the
fallback path called gateway.chat() and broadcasted the FULL content
via _replay_stream — causing the UI to see partial streamed content
followed by duplicated full content.
Fix: if `total` already contains partial content from first_chunk,
return it directly without calling gateway.chat(). Partial content is
better than duplicated content. The non-streaming fallback only runs
when no chunks were broadcasted (total is empty).
Add test_stream_breaks_after_first_chunk_returns_partial covering this
edge case: first chunk yields "部分内容", second __anext__ raises
RuntimeError. Asserts result is the partial content, gateway.chat() is
never called, and broadcast_event is called exactly once (for the
first chunk only).
0daa4d21b0