181 optional string param lowers

// PINS: `?string` in a tor parameter lowers to `?[]const u8` — the optional
// wrapper goes through the same lowering door as bare `string`. Before the
// fix, `?string` leaked verbatim into the emitted Input struct:
//   error: use of undeclared identifier 'string'
// Found by koru-libs/ai's `system: ?string` after its []const-u8 → string
// dialect migration.

~import std/io

~pub tor greet { name: string, title: ?string } -> string

~proc greet|zig {
    _ = name;
    if (title) |t| {
        return t;
    }
    return "untitled";
}

~greet(name: "ada", title: null): t |> std/io:print.ln("first: {{ t:s }}")

~greet(name: "ada", title: "countess"): u |> std/io:print.ln("second: {{ u:s }}")