refactor: update reducer calls to use pointer argument in test

Co-authored-by: aider (deepseek/deepseek-coder) <aider@aider.chat>

test_engine.c

@@ -810,21 +810,21 @@ void test_midi_clip_full_cycle(void) {
     Action action = { .type = ACTION_MIDI_CLIP_TRIGGER, .data.midi_clip_trigger = { .clip_index = 0 } };
     
     // Empty -> Recording
-    *state = reducer(*state, action);
+    reducer(state, action);
     assert(state->midi_clips[0].state == CLIP_RECORDING);
     
     // Recording -> Looping
     state->midi_clips[0].event_count = 20;
-    *state = reducer(*state, action);
+    reducer(state, action);
     assert(state->midi_clips[0].state == CLIP_LOOPING);
     assert(state->midi_clips[0].event_count == 20);
     
     // Looping -> Stopped
-    *state = reducer(*state, action);
+    reducer(state, action);
     assert(state->midi_clips[0].state == CLIP_STOPPED);
     
     // Stopped -> Looping
-    *state = reducer(*state, action);
+    reducer(state, action);
     assert(state->midi_clips[0].state == CLIP_LOOPING);
     
     destroy_test_state(state);