The GFM → Telegram-row-group rewriter previously joined every line in
every row with a blank line ("\n\n".join(rendered_rows)), which made
multi-column tables explode into one-bullet-per-paragraph walls on
mobile. It also emitted the row heading twice when the table had no
row-label column: once as the standalone bold heading and once again
as the first labeled bullet (heading == headers[0] == data_cells[0]).
This commit:
* Uses single newlines between the heading and its bullets within a
row-group, and a blank line only BETWEEN row-groups.
* Skips any bullet whose value duplicates the heading text when the
table has no row-label column (the heading already carries that
information). Tables WITH a row-label column are unaffected since
the heading comes from the label cell and never duplicates a header.
Updated existing test assertions accordingly and added two regression
tests: one that reproduces the screenshot bug (wide five-column "Plays"
comparison table) and one that pins the row-label-column behavior so
the dedup logic doesn't accidentally swallow real data.
tests/gateway/test_telegram_format.py: 101 passed