feat: Add IRC channel integration

[amirmamaghani]

Summary

Add IRC as a new picoclaw channel (pkg/channels/irc/), enabling bots to connect to IRC servers, join channels, respond to mentions, and handle DMs.

Motivation

IRC remains widely used in open-source, DevOps, and technical communities. Adding IRC support would let picoclaw bots serve users on Libera.Chat, OFTC, private IRC networks, and self-hosted servers (Ergo, UnrealIRCd, etc.) alongside existing channels like Discord, Telegram, and Slack.

Proposed Design

Follow the existing channel pattern (embed BaseChannel, implement Channel interface, register via init() factory).

Config

{
  "channels": {
    "irc": {
      "enabled": true,
      "server": "irc.libera.chat:6697",
      "tls": true,
      "nick": "mybot",
      "password": "",
      "nickserv_password": "",
      "sasl_user": "",
      "sasl_password": "",
      "channels": ["#mychannel"],
      "allow_from": [],
      "group_trigger": { "mention_only": true }
    }
  }
}

Library

github.com/ergochat/irc-go — specifically ircevent for connection management, reconnection, PING/PONG keepalive, and SASL. Maintained by the Ergo IRC server team.

Key behaviors

• Auth: SASL > NickServ > server password (in priority order)
• Inbound: PRIVMSG events → parse nick/target/content → DM vs channel → mention detection → HandleMessage
• Outbound: conn.Privmsg(target, line) — split on newlines, respect 512-byte IRC line limit via WithMaxMessageLength(400)
• Reconnection: Handled by ircevent.Connection.Loop() with built-in backoff
• Mention detection: nick: / nick, prefix (standard IRC convention) + word-boundary match. Uses conn.CurrentNick() to handle nick collisions
• Rate limiting: "irc": 2 in channelRateConfig (~2 msg/sec, safe for most networks)

Not implemented

IRC doesn't support typing indicators, message editing, placeholders, streaming, reactions, or media uploads — so none of the optional capability interfaces apply.

Files

Action	File
Modify	pkg/config/config.go — add IRCConfig struct + field to ChannelsConfig
Modify	pkg/channels/manager.go — add rate config + initChannel block
Modify	cmd/picoclaw/internal/gateway/helpers.go — add blank import
Create	pkg/channels/irc/init.go — factory registration
Create	pkg/channels/irc/irc.go — struct, constructor, Start/Stop/Send
Create	pkg/channels/irc/handler.go — PRIVMSG handler, mention helpers

Happy to submit a PR for this if there's interest.