Feat: clean the codebase as much as possible

src/input/modal.rs

@@ -208,7 +208,7 @@ pub(super) fn handle_modal_input(ctx: &mut InputContext, key: KeyEvent) -> Input
                         std::thread::Builder::new()
                             .name("sample-preload".into())
                             .spawn(move || {
-                                crate::init::preload_sample_heads(preload_entries, sr, &registry);
+                                crate::engine::preload_sample_heads(preload_entries, sr, &registry);
                             })
                             .expect("failed to spawn preload thread");
                     }