051 kebab event field

// PIN (kebab-stdlib-restructure): a kebab field `a-thing` must be in scope
// inside the proc as bare snake `a_thing` (field mangle, no prefix — fields are
// struct-scoped). RED today — `-` rejected in the field decl. Mirrors the
// field-in-scope pattern of std/io:println (`text` field used directly).
const std = @import("std");
~import std/io

~event my-stuff { a_thing: []const u8 }
~proc my-stuff|zig {
    std.debug.print("{s}\n", .{a_thing});
}

~my-stuff(a_thing: "field ok")