105 narrowing keeps plain field

// FEATURE SPEC: discharging the sole obligation field of {h!, n:i64} leaves the
// plain data behind — s collapses to the scalar n, still readable via s.n. Pins
// that discharge consumes only the obligation, not the plain data. RED until the
// feature lands.
~import std/io
const std = @import("std");
const Handle = struct { n: i32 };

~tor dispose { x: *Handle<!owned> }
~proc dispose|zig { std.heap.page_allocator.destroy(x); }

~tor makeMixed { id: usize } -> { h: *Handle<owned!>, n: i64 }
~proc makeMixed|zig { const h = std.heap.page_allocator.create(Handle) catch unreachable; h.* = .{ .n = 7 }; return .{ .h = h, .n = 7 }; }
~makeMixed(id: 1): s |> dispose(x: s.h): _ |> std/io:print.ln("n={{ s.n:d }}")