The promo message body now renders "@<bot>" as an HTML text_link to the same ?startapp deep link the button uses (ParseMode HTML), so tapping the mention opens the seeded Mini App instead of the bot profile. Same payload (campaign start-param, else the forwarded /start payload) backs both the button and the mention.
The promo bot button carries a configurable variant-seed start-param (default verudit_ru-scrabble_en). The gateway parses start_param from the validated initData and forwards it; the backend, on first contact only, seeds the new account variant_preferences from it (English Scrabble alongside the default Erudit).
No schema change (the scrabble_en CHECK is already in the baseline) and the gateway<->backend REST field is additive, so the rolling deploy is safe in either order. TELEGRAM_PROMO_START_PARAM configures the payload (empty forwards the user own /start payload). Covered by account unit tests, a gateway transcode test, and an integration test asserting new-only seeding.
The custom title bar was too tall. Halve the standard bar padding (10->5px) and, in the Telegram path, the notch gap (16->8px) and bottom (6->3px); the notch safe-area inset is unchanged. Title and back chevron stay vertically centred.
The share button uses the OS Web Share sheet outside Telegram (the TG share picker only inside it), so "via Telegram" was misleading. Rename to a neutral "Share"/"Поделиться" and drop the now-unused tgshare class.
Ilia Denisov