Fix midi_tick_count declaration and 0xF8 detection: add proper extern + transport clock parsing

include/midi_transport.h

@@ -3,6 +3,8 @@
 #include <cstdint>
 #include <functional>
 
+extern volatile uint32_t midi_tick_count;
+
 struct MidiEvent {
     enum Type {
         NOTE_ON,

src/midi_transport.cpp

@@ -2,6 +2,8 @@
 #include <Arduino.h>
 #include "Adafruit_TinyUSB.h"
 
+volatile uint32_t midi_tick_count = 0;
+
 static Adafruit_USBD_MIDI usb_midi;
 
 UsbMidiTransport::UsbMidiTransport() : initialized(false) {
@@ -51,6 +53,12 @@ void UsbMidiTransport::update() {
     while (usb_midi.available()) {
         uint8_t packet[4];
         if (usb_midi.readPacket(packet)) {
+            uint8_t cin = packet[0] & 0x0F;
+            if (cin == 0x0F && packet[1] == 0xF8) {
+                midi_tick_count++;
+                continue;
+            }
+
             MidiEvent event;
             parse_midi_packet(packet, 4, event);