124 effect arm cannot issue obligation

// Per-arm obligation rule (the multi-arm sibling of 400_107): each resume arm
// IS a resume, so an arm that ISSUES an obligation (`| granted *R<active!>`)
// would hand the proc a fresh obligation per firing that escapes the firing
// un-discharged — incoherent at 0-to-N firing. Rejected at the SIGNATURE
// level, per arm, without inspecting any body. Arm-DISCHARGE (`<!state>`)
// stays coherent, mirroring 400_106.
const std = @import("std");
const Resource = struct { id: usize };
var global_r = Resource{ .id = 99 };

~pub tor borrow { n: usize }
! lend usize
    | granted *Resource<active!>
    | denied
| done usize
~proc borrow|zig {
    const r = lend(n);
    _ = r;
    return .{ .done = n };
}

~borrow(n: 1)
! lend _ => denied
| done d |> _