v0.3.1

Fixed

• Installs on Intel Macs again, and with an Intel (x86_64) Python on Apple Silicon. cryptography 49, which Google's auth library needs, ships macOS wheels for arm64 only, so there it was built from source: that fails without Rust, or builds a module that does not load and leaves the MCP server stuck at "Connection closed". On Intel macOS gmail-agent now installs cryptography 48, the last release with Intel wheels. Other platforms are unchanged.