Message Filter Generator

[GenerateMessageFilter] creates a typed MessageFilter<TPayload> factory from ordered static predicate methods.

[GenerateMessageFilter(typeof(OrderCommand), FactoryName = "Create", FilterName = "order-fraud-screen")]
public static partial class GeneratedOrderFilter
{
    [MessageFilterRule("trusted-customer", 10)]
    private static bool IsTrusted(Message<OrderCommand> message, MessageContext context)
        => message.Payload.CustomerTier == "trusted";
}

Rules must be static methods returning bool with (Message<TPayload>, MessageContext) parameters. Duplicate rule names or orders are reported at compile time.