fix: add main to radix gpu test

tests/gpu/radix.rs

@@ -0,0 +1,38 @@
+use std::sync::{
+    Arc,
+    Mutex,
+};
+
+use bevy::{
+    prelude::*,
+    app::AppExit,
+    core::FrameCount,
+    render::view::screenshot::ScreenshotManager,
+    window::PrimaryWindow,
+};
+
+use bevy_gaussian_splatting::{
+    GaussianCloud,
+    GaussianSplattingBundle,
+    random_gaussians,
+};
+
+use _harness::{
+    TestHarness,
+    test_harness_app,
+    TestStateArc,
+};
+
+mod _harness;
+
+
+fn main() {
+    // let mut app = test_harness_app(TestHarness {
+    //     resolution: (512.0, 512.0),
+    // });
+
+    // app.add_systems(Startup, setup);
+    // app.add_systems(Update, capture_ready);
+
+    // app.run();
+}