056 union per member consume marker

// Library module: handle
// Demonstrates per-member consume markers in phantom state unions
// Each union member carries its own ! prefix to indicate obligation discharge

const std = @import("std");

// Handle type with phantom states
const Handle = struct {
    id: i32,
};

// Open a handle - produces obligation (must be finalized)
~pub event open {}
| opened *Handle<opened!>

~proc open|zig {
    std.debug.print("Opening handle\n", .{});
    const allocator = std.heap.page_allocator;
    const h = allocator.create(Handle) catch unreachable;
    h.* = Handle{ .id = 42 };
    return .{ .opened = h };
}

// Start closing - explicitly discharges opened! and produces closing! obligation
~pub event start-close { h: *Handle<!opened> }
| closing *Handle<closing!>

~proc start-close|zig {
    std.debug.print("Starting close: {d}\n", .{h.id});
    return .{ .closing = h };
}

// Finalize - per-member consume markers: !opened discharges opened!, !closing discharges closing!
~pub event finalize { h: *Handle<!opened|!closing> }

~proc finalize|zig {
    std.debug.print("Finalizing handle: {d}\n", .{h.id});
}