Surface the usage_metadata that PR #1218 added to the streaming API.
A compact indicator in the chat header shows cumulative tokens consumed
per thread, with a tooltip breakdown of input/output/total counts.
Co-authored-by: Matt Van Horn <455140+mvanhorn@users.noreply.github.com>
Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>
Co-authored-by: Willem Jiang <willem.jiang@gmail.com>
Matt Van Horn