Closes the #32029 gap: TelegramAdapter.send_voice passed captions raw with
no parse_mode, so auto-TTS captions (which carry the agent's markdown
reply) showed literal *asterisks*, backticks and [links](...). Captions
are now formatted to MarkdownV2 via the adapter's format_message when the
formatted text fits Telegram's 1024-char caption cap, with fallback to the
plain truncated caption when formatting overflows or the Bot API rejects
the entities (mirrors the text-send markdown fallback ladder).
Fixes#32029
ee15e04803