The `replyToMessageIdForPayload` was computed once outside the chunk
and media loops, so all chunks received the same reply-to ID even when
replyToMode was set to "first". This replaces the static binding with
a lazy `resolveReplyTo()` function that checks `hasReplied` at each
send site, and updates `hasReplied` immediately after the first
successful send.
Fixes#31039
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>