Fix: move if/else outside defmodule to avoid Zig macro expansion

Elixir expands macros in both branches of a module-level if/else,
causing 'use Zig' to fail when Zigler isn't installed even if the
precompiled path is taken. Moving the conditional to the file top
level (outside defmodule) ensures only the matching branch is evaluated.

Author: bcardarella

lib/tailwind_compiler/nif.ex

@@ -1,7 +1,7 @@
-defmodule TailwindCompiler.NIF do
-  @moduledoc false
+if TailwindCompiler.Native.use_precompiled?() do
+  defmodule TailwindCompiler.NIF do
+    @moduledoc false
 
-  if TailwindCompiler.Native.use_precompiled?() do
     @on_load :__load_nif__
 
     @doc false
@@ -15,7 +15,11 @@ defmodule TailwindCompiler.NIF do
 
     def validate(_tokens),
       do: :erlang.nif_error(:not_loaded)
-  else
+  end
+else
+  defmodule TailwindCompiler.NIF do
+    @moduledoc false
+
     use Zig,
       otp_app: :tailwind_compiler,
       nifs: [compile: [:dirty_cpu], validate: [:dirty_cpu]],