[keel,nostalgia] Make core calls take Context references instead of pointers

src/nostalgia/player/app.cpp

@@ -34,7 +34,7 @@ static void keyEventHandler(turbine::Context &tctx, turbine::Key key, bool down)
 
 ox::Error run(ox::UniquePtr<ox::FileSystem> &&fs) noexcept {
 	oxRequireM(tctx, turbine::init(std::move(fs), "Nostalgia"));
-	oxRequireM(cctx, core::init(tctx.get()));
+	oxRequireM(cctx, core::init(*tctx));
 	constexpr ox::FileAddress SceneAddr("/Scenes/Chester.nscn");
 	oxRequire(scn, keel::readObj<scene::SceneStatic>(tctx->keelCtx, SceneAddr));
 	turbine::setUpdateHandler(*tctx, updateHandler);