Cancelled outbound transfers previously returned from the streaming loop without
terminating the QUIC send half. A whole-file receiver relies on the stream
ending to distinguish EOF from an in-progress body, so cancellation could leave
it waiting on a truncated transfer until its own timeout fired.
Reset the send stream on every cancellation branch, including cancellation
while waiting for the final close acknowledgement. A reset is deliberately used
instead of a graceful close so truncated whole-file transfers cannot be
misinterpreted as a valid EOF.
Test Plan:
- just test
- just clippy
- git diff --check
Refs: Claude review finding #1
ddidderr
f89ff9ceea
