Outbound MEDIA video/document tags on the Discord non-streaming path
were extracted (stripped from the visible text) but never delivered:
no attachment, no error, and no dispatch log line (#66797). The
open-handle discord.File plus singular file= form could race Discord's
multipart encoder after an earlier image batch on the same channel and
return a successful message carrying zero attachments.
Fix _send_file_attachment (used by send_video/send_document/
send_image_file) to:
- use a path-based discord.File via the plural files=[...] kwarg, the
same pattern as the working send_multiple_images batch path;
- pre-flight os.path.isfile and return a File not found result instead
of raising deep inside discord.File;
- fail loud when Discord accepts the message but attaches nothing, so
the dispatch loop surfaces a warning rather than a silent drop;
- add INFO dispatch logs (base non-image MEDIA fan-out, video send, and
file attachment) so a MEDIA:.mp4 cannot vanish without a trace.
Tests (tests/gateway/test_discord_send.py):
- path-based files=[...] kwarg used, singular file= unset;
- fail-loud when the returned message has no attachments;
- missing file fails fast without resolving the channel;
- forum-parent delivery routes through create_thread with files=[...];
- end-to-end image+video response routes the mp4 to send_video while
images still batch.
Fixes#66797
8eb29a1bb9