Chat SDK adapters use prefixed platform IDs (e.g. "telegram:6037840640",
"discord:guildId:channelId") but users provide raw IDs during setup.
Without the prefix, the router can't match the registered messaging group
to incoming messages and silently drops them.
register.ts now auto-prefixes with the channel type if not already present.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>