Discord auto-creates a managed role for each bot. When a bot is not
visible in the channel member list (common in new channels or when
multiple bots share a guild), users can only @mention the role instead
of the user. The role mention format <@&roleID> was not recognized,
causing the bot to silently ignore the message.
Fix by:
- Caching bot's managed role ID on Ready and GuildCreate events
- Checking m.MentionRoles and <@&roleID> content in addition to
m.Mentions and <@botID> content
- Stripping role mention tags from message content
- Adding IntentsGuilds to receive GuildCreate events for role lookup
Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>