* fix(discord): reject empty outbound messages
* test(discord): cover empty final reply backfill state
Missed-message backfill decides what to replay from discord_messages, so
a dropped final reply must be recorded as failed by the new guard the
same way the exception path records one — otherwise the reply is both
never sent and never retried.
Co-authored-by: Jony <619963502@qq.com>
* chore: map 619963502@qq.com to zyz619963502zyz for PR #73449 salvage
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Co-authored-by: Jony <619963502@qq.com>
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