Add beads-native queue management commands to gt mail:
- gt mail queue create <name> --claimers <pattern>
- gt mail queue show <name>
- gt mail queue list
- gt mail queue delete <name>
Also enhanced QueueFields struct with CreatedBy and CreatedAt fields
to support queue metadata tracking.
Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>