fix: strip @botname from commands so /new@TigerNanoBot resolves correctly (#3581)

Commands sent directly to the bot in groups include @botname suffix
(e.g. /compress@TigerNanoBot). get_command() now strips the @anything
part before lookup, matching how Telegram bot menu generates commands.
Fixes all slash commands silently doing nothing when sent with @mention.

Co-authored-by: MacroAnarchy <MacroAnarchy@users.noreply.github.com>

gateway/platforms/base.py

@@ -333,7 +333,10 @@ class MessageEvent:
             return None
         # Split on space and get first word, strip the /
         parts = self.text.split(maxsplit=1)
-        return parts[0][1:].lower() if parts else None
+        raw = parts[0][1:].lower() if parts else None
+        if raw and "@" in raw:
+            raw = raw.split("@", 1)[0]
+        return raw
     
     def get_command_args(self) -> str:
         """Get the arguments after a command."""