Expand description
The token-expander-axis-derive crate defines the custom #[derive(TokenExpansionAxis)]
procedural macro. It reads the enum, extracts the #[system_message_goal("...")]
and #[axis("axis_name" => "axis_description")] attributes, and implements
the SystemMessageGoal, AxisName, and AxisDescription traits from the
token-expander-axis crate.