* fix(channels): resolve reply artifacts off the event loop
_handle_chat_on_thread and _handle_streaming_chat called
_prepare_artifact_delivery inline. For every presented file it resolves
the virtual path (realpath), resolves the outputs root, and checks the
file with is_file and stat, all on the Gateway loop that also serves
every other channel and request.
Run it through asyncio.to_thread on both reply paths, and anchor both
through the real manager under the strict blocking-I/O gate.
* docs(changelog): reference #7594 for the off-loop reply artifact resolution
* docs(changelog): drop the duplicate #7580 link definition in the zh changelog
---------
Co-authored-by: Willem Jiang <willem.jiang@gmail.com>
77d0fc9d69