[FEATURE] Gmail connector: let forward create a draft instead of sending

What happened: I asked Claude to prepare a forward of an email (one carrying a PDF attachment) for me to review and send. The connector's forward tool sends straight away and has no draft option. create_draft can't forward a message, and its own attachments have to be passed as encoded text (see #95688). So Claude couldn't prepare the forward at all, and I had to build it by hand in Gmail.

Expected: a way to save a forward as a draft. Either a draft: true option on forward, or a forwardMessageId on create_draft that brings across the original message's attachments, the same way replyToMessageId works for replies.

Why it matters: a common safe pattern is "Claude drafts, the human sends". Without a draft option for forwards, any workflow that must never send on its own can't forward at all, even when the email it needs to pass on (an invoice, a certificate) is already sitting in the mailbox.

Environment: Claude desktop app (Code tab), Windows 11, Gmail connector.

Related: #95688, #28575