070 effect branch minimal

// Test: minimum effect-branch program — proc yields, consumer handles.
//
// `! pong []const u8` is an effect branch; the proc body calls `pong(msg)`
// which transfers control to the consumer's `! pong reply |> ...` handler,
// runs it, then returns. No terminal `|` branches — this is a void event
// with one effect operation.

~import std/io

const std = @import("std");

~pub event ping { msg: []const u8 }
! pong []const u8

~proc ping|zig {
    pong(msg);
}

~ping(msg: "hello effect branches")
! pong reply |> std/io:print.blk {
    {{ reply:s }}
}