100 effect obligation discharged in firing

// REQUIREMENT (effect-branch obligations, simple/in-firing case — the `for` model):
// An effect `! each` generator yields per element. The consumer's handler may
// create an obligation AND discharge it within that same firing. Because the
// `! each` signature carries NO `<state!>` resume, an obligation born in the
// handler cannot escape — it MUST be settled in-firing. Here it is (create →
// destroy), so this is balanced and should run.
~import std/build
~std/build:requires { exe.linkLibC(); }
const std = @import("std");
const Resource = struct { id: usize };
const allocator = std.heap.c_allocator;

~event create { id: usize }
| created *Resource<active!>
~proc create|zig {
    const r = allocator.create(Resource) catch unreachable;
    r.* = Resource{ .id = id };
    return .{ .created = r };
}

~event destroy { r: *Resource<!active> }
~proc destroy|zig {
    std.debug.print("freeing {}\n", .{r.id});
    allocator.destroy(r);
}

~pub event gen { n: usize }
! each usize
| done usize
~proc gen|zig {
    for (0..n) |i| { each(i); }
    return .{ .done = n };
}

~gen(n: 3)
! each i |> create(id: i)
    | created r |> destroy(r)
| done _ |> _