Add `lark-cli mail +draft-send` shortcut that takes one or more existing
draft IDs and sends each via POST /drafts/:draft_id/send sequentially.
Per-draft failures are isolated and aggregated into a structured output;
fatal failures (auth, permission, network, mailbox quota) abort the
entire batch immediately while recoverable failures honor --stop-on-error.
Also extend internal/output with six mail-send-specific errno constants
(LarkErrMailboxNotFound=4013, LarkErrMailSendQuota{User,UserExt,TenantExt},
LarkErrMailQuota, LarkErrTenantStorageLimit) consumed by isFatalSendErr.
Risk is "high-risk-write" so the framework's --yes gate applies; the
shortcut declares only the minimal mail:user_mailbox.message:send scope
to avoid asking users for permissions it does not need.
