Screen finding on #131927: when QQ media delivery failed (stale local
path, daily upload quota, oversized file, or any upload/API error),
_send_qqbot's media path returned a bare error and the caption/message
text was never delivered — a regression against main, where QQ
text+media degraded to the text delivered plus a 'MEDIA attachments
were omitted' warning.
- collect per-attachment failures as warnings and keep delivering
(previously the first failed attachment aborted the whole send)
- when nothing was deliverable, fall back to sending the text or the
caption standalone, matching the pre-media generic path
- surface collected warnings on the final result (and on error returns)
Tests: missing-file, upload-quota and generic-delivery failure flows
assert the text still lands exactly once with a warning (red on the
PR head before this fix).
ebadb5462e