test: remove skipped custom field slug lookup test

test/membership/custom_field_slug_test.exs

@@ -192,21 +192,5 @@ defmodule Mv.Membership.CustomFieldSlugTest do
     end
   end
 
-  describe "slug-based lookup (future feature)" do
-    @tag :skip
-    test "can find custom field by slug", %{actor: actor} do
-      {:ok, custom_field} =
-        CustomField
-        |> Ash.Changeset.for_create(:create, %{
-          name: "Test Field",
-          value_type: :string
-        })
-        |> Ash.create(actor: actor)
-
-      # This test is for future implementation
-      # We might add a custom action like :by_slug
-      found = Ash.get!(CustomField, custom_field.slug, load: [:slug], actor: actor)
-      assert found.id == custom_field.id
-    end
-  end
+  # Slug-based lookup (e.g. CustomField by slug) is not implemented; primary read uses ID.
 end