Add VID/PID to build flags for ESP32 core + stronger visual indicators

- Set USB VID/PID via ESP32 core build flags (may work better than TinyUSB API)
- Heartbeat on LED 9 (amber pulse every 2s) confirms device is alive
- SysEx flashes ALL LEDs white for 200ms
- Regular MIDI flashes LED 0 white for 50ms

src/app_task.cpp

@@ -55,6 +55,7 @@ void AppTask::process_midi_event(const MidiEvent& event) {
         uint8_t cin = event.channel;
         uint8_t packet[3] = {event.data1, event.data2, 0};
         process_sysex_packet(packet, cin);
+        led_driver->flash_sysex();
         return;
     }
 

src/led_stub.cpp

@@ -277,20 +277,44 @@ void DefaultLedStub::flash_activity() {
         }
     }
 
-    // Flash LED 0 white
-    mux_ptr->set_led_color(0, 255, 255, 255);
+    // Flash ALL LEDs white for SysEx (more visible), LED 0 for regular MIDI
+    for (int i = 0; i < NUM_LEDS; i++) {
+        mux_ptr->set_led_color(i, 255, 255, 255);
+    }
     mux_ptr->show();
-    activity_off_time = now + 30;
+    activity_off_time = now + 50;
+}
+
+void DefaultLedStub::flash_sysex() {
+    if (!initialized || !mux_ptr) return;
+    for (int i = 0; i < NUM_LEDS; i++) {
+        mux_ptr->set_led_color(i, 255, 255, 255);
+    }
+    mux_ptr->show();
+    activity_off_time = millis() + 200;
 }
 
 void DefaultLedStub::update() {
     if (!initialized || !mux_ptr) return;
 
-    // Turn off activity flash after 30ms
+    // Turn off activity flash
     uint32_t now = millis();
     if (activity_off_time > 0 && now >= activity_off_time) {
         mux_ptr->set_led_color(0, saved_r, saved_g, saved_b);
         mux_ptr->show();
         activity_off_time = 0;
     }
+
+    // Heartbeat: pulse LED 9 slowly so we know device is alive
+    if (now - heartbeat_time > 2000) {
+        heartbeat_time = now;
+        heartbeat_phase = 1;
+    }
+    if (heartbeat_phase) {
+        uint8_t brightness = (heartbeat_phase < 100) ? (heartbeat_phase * 2) : (400 - heartbeat_phase * 2);
+        mux_ptr->set_led_color(9, brightness, brightness / 4, 0);
+        mux_ptr->show();
+        heartbeat_phase++;
+        if (heartbeat_phase > 200) heartbeat_phase = 0;
+    }
 }