fix: stabilize desktop audio playback

src/native_core/bus/tests/apu.rs

@@ -312,3 +312,23 @@ fn dmc_playback_updates_output_level_from_sample_bits() {
 
     assert!(bus.apu.dmc_output_level < initial);
 }
+
+#[test]
+fn pulse_channel_outputs_become_audible_after_setup() {
+    let mut bus = NativeBus::new(Box::new(StubMapper));
+    bus.write(0x4015, 0x01); // enable pulse1
+    bus.write(0x4000, 0b0101_1111); // 25% duty, constant volume=15
+    bus.write(0x4002, 0x08); // low timer period, not sweep-muted
+    bus.write(0x4003, 0x00); // reload length + reset duty sequencer
+
+    let mut saw_non_zero = false;
+    for _ in 0..64u32 {
+        bus.clock_cpu(1);
+        if bus.apu_channel_outputs().pulse1 > 0 {
+            saw_non_zero = true;
+            break;
+        }
+    }
+
+    assert!(saw_non_zero, "pulse1 never produced audible output");
+}