Adds a shared HTTP server (port 3000, configurable via WEBHOOK_PORT)
that routes incoming webhooks to the correct Chat SDK adapter by path
(e.g. /api/webhooks/slack, /api/webhooks/teams). Required by Slack,
Teams, GitHub, Linear, and other non-gateway adapters.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
The Discord adapter fails to start without all three env vars. Also
fix platform ID format docs to show discord:{guildId}:{channelId}.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>