Gmail connector: send_email tool missing despite gmail.send OAuth scope being requested

### Summary

The Gmail connector (available in the Engineering plugin) requests the `gmail.send` OAuth scope during authorization, but the MCP server does **not** expose a `send_email` (or equivalent) tool. Users who connect Gmail expect to be able to send emails via Claude — this is a confusing gap where permission is explicitly requested but the capability is unavailable.

### Affected Connector

- **Plugin:** Engineering (`engineering@knowledge-work-plugins`)
- **Connector:** Gmail
- **MCP server ID:** `9ef7e5d1-a7cf-4104-bcfd-129d27017b8e`
- **Platform:** Claude Desktop (Cowork mode), Windows ARM64

### Available Tools (confirmed via tool introspection)

`create_draft`, `search_threads`, `get_thread`, `list_drafts`, `list_labels`, `create_label`, `label_message`, `label_thread`, `unlabel_message`, `unlabel_thread`, `apply_sensitive_message_label`, `apply_sensitive_thread_label`

### Missing Tool

`send_email` (or `send_draft` / `send_message`)

### Impact

During the OAuth consent flow, the `gmail.send` scope is explicitly requested — so users expect send capability. Without it, Claude can only create drafts that the user must then open in Gmail to send manually. This significantly limits the connector's usefulness for automated workflows.

### Suggested Fix

Implement a `send_email` tool that uses the already-authorized `gmail.send` scope, or alternatively a `send_draft` tool that sends an existing draft by ID.

```python
# Example: send_draft by draft ID
def send_draft(draft_id: str) -> dict:
# Uses gmail.send scope already authorized
return gmail_service.users().drafts().send(userId='me', body={'id': draft_id}).execute()
```

### Workaround

Currently the only workaround is using browser automation (Claude in Chrome) to open Gmail and click Send manually — which defeats the purpose of the connector.

### Related

- Bug report also filed with Anthropic support (support@anthropic.com).———