Macro channel 

macro_rules! channel {
    ($plugin_id:ident : $msg_ty:ty) => { ... };
}

Creates a channel plugin for a message type.

The channel! macro creates a plugin that:

• exposes a ChannelSpec for the editor and persistence layer
• provides a channel factory for reconstruction
• registers itself through the plugin inventory
• makes the message type available in the editor’s Channels section

Example:

#[derive(Debug, Clone, Copy, Default, TypeHash, Message)]
pub struct VehicleState {
    pub ready: bool,
    pub parked: bool,
    pub speed_mps: f32,
}

beetry_plugin::channel! {VehicleStateChannel: VehicleState}