Thin wrapper around the Telegram Bot API using babashka/http-client.

Telegram Bot API reference: https://core.telegram.org/bots/api

Telegram-facing primitives:
- `get-updates`      long-poll for incoming messages
- `send-message!`    send text back (auto-splits at Telegram's limit)
- `send-chat-action!`  show 'typing...' while the LLM works
- `set-my-commands!` install the slash-command menu shown by Telegram

Telegram frontend for vis - long-polling loop that hands each incoming
message to the canonical in-process gateway and ships the answer back.

Each Telegram chat maps to a `:telegram` gateway session by external chat id.
One process can serve many chats; the gateway serializes asks per-session and
emits the same event/turn machinery used by TUI, web, and transport clients.