feat(discord): @everyone/@here should optionally count as a bot mention (allow_user_messages=mentions drops mass pings) #1538

Problem

With allow_user_messages = "mentions", a user message containing only @everyone (or @here) is silently dropped: is_mentioned = msg.mentions_user_id(bot_id) only checks the mentions[] array, and Discord mass pings populate mention_everyone, not mentions[].

In multi-bot deployments this makes "summon all agents" impossible — users must type every bot mention explicitly (@BotA @BotB @BotC ...). Bot operators commonly want an @everyone ping to wake all online bots.

Current behavior

discord.rs:480  is_mentioned = msg.mentions_user_id(bot_id)
discord.rs:783  if !is_mentioned && !is_dm { AllowUsers::Mentions => return }

@everyone message → is_mentioned = false → dropped before reaching the agent. Verified on 0.10.0-beta.4 release binary (macOS x86_64): 6 bot instances, all silent on @everyone.

Proposal

Either:

1. Treat msg.mention_everyone as a mention in mentions mode (simplest: is_mentioned = msg.mentions_user_id(bot_id) || msg.mention_everyone), or
2. Add a config toggle, e.g. [discord] everyone_mentions_bot = true (default false → backward compatible per project rules), or
3. A new AllowUsers variant that counts mass pings as mentions.

Option 2 preserves existing deployments' behavior exactly while enabling the use case.

Notes

• Bot-to-bot relays partially work today (allow_bot_messages = "mentions" + trusted_bot_ids): one bot can wake others by @mentioning them in a reply. But the initial human → bots hop still needs an explicit per-bot mention.
• Happy to test a patch on our 6-bot deployment.