refactor: replace static MIDI event array with dynamic allocation

dispatcher.h

@@ -56,8 +56,9 @@ typedef struct {
 
 typedef struct {
     ClipState state;
-    MidiEvent events[MAX_MIDI_EVENTS];
+    MidiEvent *events;  // Dynamically allocated
     int event_count;
+    int max_events;     // Allocated size
     int read_index;
     char channel_name[64];  // per-channel name for MIDI grid
 } MidiClip;