Adds built-in Tlon (Urbit) channel plugin to support decentralized messaging on the Urbit network.
Features:
- DM and group chat support
- SSE-based real-time message monitoring
- Auto-discovery of group channels
- Thread replies and reactions
- Integration with Urbit's HTTP API
This resolves cron delivery issues with external Tlon plugins by making it a first-class built-in channel alongside Telegram, Signal, and other messaging platforms.
Implementation includes:
- Plugin registration via ClawdbotPluginApi
- Outbound delivery with sendText and sendMedia
- Gateway adapter for inbound message handling
- Urbit SSE client for event streaming
- Core bridge for Clawdbot runtime integration
Co-authored-by: William Arzt <william@arzt.co>
