Route messages and replies to the correct Telegram forum topic via
message_thread_id. Key behaviors:
- Parse message_thread_id, is_topic_message, is_forum from incoming updates
- Thread agent sessions by "chat_id:topic_id" for forum groups only
(non-forum reply threads are excluded via is_forum guard)
- Pass message_thread_id through all send methods (text, photo, document)
- Normalize thread_id=1 (General topic) to None for sendMessage/sendPhoto/
sendDocument since Telegram rejects it, but preserve it for sendChatAction
where Telegram requires it for typing indicators
- Hoist bot_username workspace read to avoid duplicate WASM host call per
group message
Co-authored-by: Claude Opus 4.6 (1M context) <[email protected]>
