When truncate_message appends a (N/M) chunk indicator to a chunk that
had to close an in-progress fenced code block, the marker lands on the
closing fence line (``` \(1/2\) after MarkdownV2 escaping). Telegram
does not treat that as a clean closing fence and rejects the MarkdownV2,
falling back to plain text. Move the indicator onto its own line right
after the closing fence at all three legacy-send call sites.
Fixes#48517
796f618f99