Feat: add icon and reorganize desktop.rs

src/engine/sequencer.rs

@@ -165,7 +165,9 @@ impl SequencerHandle {
 
     pub fn shutdown(self) {
         let _ = self.cmd_tx.send(SeqCommand::Shutdown);
-        let _ = self.thread.join();
+        if let Err(e) = self.thread.join() {
+            eprintln!("Sequencer thread panicked: {e:?}");
+        }
     }
 }
 
@@ -873,7 +875,7 @@ fn sequencer_loop(
         let tempo = state.tempo();
 
         let sr = sample_rate.load(Ordering::Relaxed) as f64;
-        let audio_samples = audio_sample_pos.load(Ordering::Relaxed);
+        let audio_samples = audio_sample_pos.load(Ordering::Acquire);
         let engine_time = if sr > 0.0 {
             audio_samples as f64 / sr
         } else {