fix(gmail): allow Workspace native aliases with empty verification status

[salmonumbrella]

Summary

• allow --from when a configured send-as alias has empty verificationStatus but is Gmail-managed (no custom SMTP relay), matching Google Workspace native alias behavior
• keep rejecting explicit unverified statuses such as pending
• apply the same validation logic to both gmail send and gmail drafts create
• add regression tests for send, drafts, and the shared send-as validation helper

Fixes #406

Testing

• make fmt
• make lint
• make test