005 user event binding

// TEST: kernel view binding flows to computed branch for user events
//
// Verifies:
// 1. kernel:init creates a view binding
// 2. computed branch receives the kernel data
// 3. user-defined events can consume values from computed data

~import std/kernel
~import std/io

~std/kernel:shape(Body) {
    mass: f64,
}

~event print-mass { value: f64 }
~proc print-mass|zig {
    const std = @import("std");
    std.debug.print("mass={d}\n", .{value});
}

~std/kernel:init(Body) {
    { mass: 1.0 },
    { mass: 2.0 },
}
| kernel k |> std/kernel:self { k.mass *= 1.0 }
| computed c |> print-mass(value: c[0].mass)