docs(gmail): publish email attachments capability and host coverage (TOO-981) (#1025)

Add one documentationChunk to gmail.json (after_available_tools, below the tool list): an 'Adding attachments to emails' section covering the capability (the agent installs the one-time hook for the user on first use) and the host coverage table. Single section, no manual per-host setup instructions.

Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: EricGustin

toolkit-docs-generator/data/toolkits/gmail.json

@@ -1885,6 +1885,14 @@
       "location": "auth",
       "position": "after",
       "content": "The Arcade Gmail MCP Server uses the [Google auth provider](/references/auth-providers/google) to connect to users' Google accounts.\n---"
+    },
+    {
+      "type": "markdown",
+      "location": "after_available_tools",
+      "position": "after",
+      "content": "## Adding attachments to emails\n\nThe Gmail send, draft, and reply tools take an `attachments` parameter for local files. The agent emits only the file path; a client-side `preToolUse` hook swaps in the bytes before the request leaves your machine, so file contents never enter the model's context window.\n\nThe first time you attach a file, your agent installs the one-time hook for you after you approve. Gmail caps total message size at 25 MB.\n\nAttachments work on hosts that support a client-side pre-tool hook. On any other host the tool returns a clear error and sends nothing.\n\n| Host | Status | Notes |\n| --- | --- | --- |\n| Cursor | Supported | App, plus Cursor cloud and background agents. |\n| Claude Code | Supported | v2.0.10+. |\n| Codex CLI | Supported | v0.131+. |\n| VS Code chat (GitHub Copilot) | Supported | 1.112+, agent mode. |\n| Claude Cowork | Documented limitation | Sandboxed to one folder; the hook cannot be installed from inside it. |\n| Claude Desktop | Documented limitation | No client-side hook layer. |\n| ChatGPT desktop | Documented limitation | No client-side hook surface. |\n| Microsoft 365 Copilot | Documented limitation | No host-side rewrite hook. |",
+      "header": "## Adding attachments to emails",
+      "priority": 10
     }
   ],
   "customImports": [