The router was missing support for beads-native channel addresses.
When mail_send.go resolved an address to RecipientChannel, it set
msg.To to "channel:<name>" but router.Send() had no handler for this
prefix, causing channel messages to fail silently.
Added:
- isChannelAddress() and parseChannelName() helper functions
- sendToChannel() method that creates messages with proper channel:
labels for channel queries
- Channel validation before sending
- Retention enforcement after message creation
Also updated docs/beads-native-messaging.md with more comprehensive
documentation of the beads-native messaging system.
Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>