060 multi op fusion

// TEST: kernel/computed split — kernel ops in kernel branch, post-processing in computed
//
// The kernel branch is a closed region: only kernel:pairwise and kernel:self allowed.
// The computed branch is normal code that runs after, with access to the final data.
//
// Today these emit separate code blocks (two ptr extractions, two loop nests).
// Future: init should fuse the kernel branch into one block with one ptr extraction.
//
// Data: 3 bodies with mass = 1.0, 2.0, 3.0
// After pairwise { k.mass += k.other.mass * 0.1 }:
//   Each body is in 2 pairs, so each gets +0.2
//   → 1.2, 2.2, 3.2
// After self { k.mass *= 2.0 }:
//   → 2.4, 4.4, 6.4

~import "$std/kernel"
~import "$std/io"

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

~std.kernel:init(Body) {
    { mass: 1.0 },
    { mass: 2.0 },
    { mass: 3.0 },
}
| kernel k |>
    std.kernel:pairwise { k.mass += k.other.mass * 0.1 }
    |> std.kernel:self { k.mass *= 2.0 }
| computed c |>
    std.io:print.blk {
        mass[0]={{ c[0].mass:f }} mass[1]={{ c[1].mass:f }} mass[2]={{ c[2].mass:f }}
    }