Allow `gt mail delete` to accept multiple message IDs at once,
matching the existing behavior of archive, mark-read, and mark-unread.
Also adds --body as an alias for --message in mail reply.
Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
Allow `gt mail reply <id> "message"` in addition to `-m` flag.
This is a desire-path fix - agents naturally try positional syntax.
Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>