fix(gateway): strip @botname suffix from Telegram slash command parsing

[Kathie-yu]

Summary

Telegram clients append the bot username to slash commands (e.g. /model@MyBot_bot). get_command() does not strip this suffix, so resolve_command() fails to match and the command falls through to the agent as plain text.

This affects both group chats and DMs:

• Group chats / Supergroups: Telegram Bot API always appends @botname to disambiguate between multiple bots
• DMs: Some Telegram clients also append @botname in private chats (observed on Telegram Desktop and certain mobile client versions)

All slash commands are affected — including the new /models command proposed in #3500 (#3502, #3503), which would also fail in group chats and DMs without this fix.

Root cause

MessageEvent.get_command() in gateway/platforms/base.py extracts the command with text.split()[0][1:] — this returns model@mybot_bot instead of model. Since resolve_command("model@mybot_bot") returns None, the message bypasses command dispatch entirely.

The @username suffix is a standard Telegram Bot API convention — it is guaranteed in group chats and common in DMs depending on client implementation.

Fix

gateway/platforms/base.py: Strip everything after @ in the extracted command name (3-line change in get_command()).

cmd = parts[0][1:].lower()
if cmd and "@" in cmd:
    cmd = cmd.split("@")[0]

This is safe for all platforms — only Telegram uses the @suffix convention, and no valid command name contains @.

How to test

1. In a group chat: send /model@YourBot_bot — should now be recognized as /model
2. In a DM: send /help@YourBot_bot — should show help
3. Verify commands without @botname suffix still work normally in both chat types

Platform tested

Linux, Telegram gateway (group chats and DMs)

Related to #3500

[teknium1]

Merged via #3581 using #3550's implementation (which included tests). You were first to submit this fix — both contributors credited. Thanks!