refactor: replace DEFAULT_BPM with literal value in test

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

test_tui.c

@@ -24,7 +24,7 @@ static AppState create_test_state(void) {
     // Initialize transport
     state.transport_state = TRANSPORT_STOPPED;
     state.clock_source = CLOCK_SOURCE_INTERNAL;
-    state.bpm = DEFAULT_BPM;
+    state.bpm = 120.0;
     state.samples_per_beat = (48000 * 60.0) / DEFAULT_BPM;
     state.clock_count = 0;
     state.beat_position = 0;