141 child run nonzero exit stderr term

// PINNED BUG (2026-07-02, surfaced by koru-libs docker lift): a koru-compiled
// proc that runs std.process.Child.run and reads result.term.Exited PANICS
// ("access of union field 'Exited' while field 'Signal' is active") when the
// child exits NONZERO with STDERR CONTENT. The identical Zig compiled directly
// with `zig run` (same Zig 0.15.2) returns term = .{ .Exited = 3 } correctly.
// Nonzero-exit-with-empty-output and zero-exit-with-content both work through
// koru; only the nonzero+stderr combination corrupts the Term union tag.
// Expected (correct) behavior: the failed branch fires and prints the stderr
// text. Today: runtime panic — this test is an honest red pinning the defect.

~import std/io
const std = @import("std");

~event run-cmd { argv0: []const u8 }
| ok i32
| failed { code: i32, msg: []const u8 }

~proc run-cmd|zig {
    const allocator = std.heap.page_allocator;
    const result = std.process.Child.run(.{
        .allocator = allocator,
        .argv = &[_][]const u8{ argv0, "-c", "printf 'error message to stderr' 1>&2; exit 3" },
    }) catch |err| {
        return .{ .failed = .{ .code = -1, .msg = @errorName(err) } };
    };
    defer allocator.free(result.stdout);
    defer allocator.free(result.stderr);

    if (result.term.Exited != 0) {
        return .{ .failed = .{ .code = @intCast(result.term.Exited), .msg = result.stderr } };
    }
    return .{ .ok = 0 };
}

~run-cmd(argv0: "sh")
| ok _ |> std/io:print.ln("ok")
| failed e |> std/io:print.ln(e.msg)