085 obligation held across back edge

// PROBE for Limitation 1 (held-across, same scope): an obligation OWNED in the
// same scope as a label-fold back-edge, the fold runs over a SCALAR (never
// touches the handle), and the handle is escaped on the exit branch. h0 is live
// (uncleaned) at `@loop(c: v)` but is NOT the loop's to consume — it is held
// across and escaped on `fin`. If conservation is held-across-aware this is
// sound; if not, the back-edge check false-flags h0 as a dropped obligation.
// Mirrors 330_074 exactly, but the carried slot is a scalar and h0 is held.
const std = @import("std");
const Handle = struct { n: i32 };

~event make {}
| made *Handle<owned!>
~proc make|zig {
    const h = std.heap.page_allocator.create(Handle) catch unreachable;
    h.* = .{ .n = 0 };
    return .{ .made = h };
}

~event icount { c: i32 }
| more i32
| fin i32
~proc icount|zig {
    if (c < 3) return .{ .more = c + 1 };
    return .{ .fin = c };
}

~event dispose { h: *Handle<!owned> }
~proc dispose|zig {
    std.debug.print("n={}\n", .{h.n});
    std.heap.page_allocator.destroy(h);
}

~event spin {}
| finished *Handle<owned!>

~spin = make()
| made h0 |> #loop icount(c: 0)
    | more v |> @loop(c: v)
    | fin _ => finished h0

~spin()
| finished hf |> dispose(h: hf)