v0.5.5

Add messages draft command for creating draft emails (#51)

Wire up draft creation through the existing Gmail Drafts plumbing. The new
`messages draft` command mirrors `messages send` flags but calls
Users.Drafts.Create instead of Messages.Send, returning the created draft ID.
Shared MIME assembly is factored out of SendParts/runMessagesSend so send and
draft stay in sync.

https://claude.ai/code/session_01BWTsRtPMNRbk9mjzYbBHDa

Co-authored-by: Claude <noreply@anthropic.com>