Convert to PlatformIO/Arduino format

- Replace ESP-IDF structure with PlatformIO (platformio.ini)
- Move source files to src/ and include/
- Move libraries to lib/ directory
- Replace FreeRTOS with Arduino task/vTaskDelay
- Use Arduino MIDI library instead of raw TinyUSB
- Dual-core: MIDI on core 0, controller on core 1

src/main.cpp

@@ -0,0 +1,69 @@
+// Loopy MIDI Controller - Phase 1
+// ESP32-S3 USB MIDI Foot Controller
+
+#include <Arduino.h>
+#include "midi_transport.h"
+#include "led_stub.h"
+#include "switch_stub.h"
+#include "app_task.h"
+
+// Hardware instances
+DefaultLedStub led_driver;
+DefaultSwitchStub switch_driver;
+UsbMidiTransport midi_transport;
+
+// Controller task
+AppTask controller(&led_driver, &switch_driver, &midi_transport);
+
+// FreeRTOS task handles
+TaskHandle_t midi_task_handle = NULL;
+
+// MIDI processing task (runs on core 0)
+void midi_task(void* parameter) {
+    Serial.println("[TASK] MIDI task started on core 0");
+    
+    while (true) {
+        midi_transport.update();
+        vTaskDelay(1);  // Yield to other tasks
+    }
+}
+
+void setup() {
+    Serial.begin(115200);
+    delay(1000);
+    
+    Serial.println("=============================");
+    Serial.println("Loopy MIDI Controller v0.1");
+    Serial.println("Phase 1: USB MIDI");
+    Serial.println("=============================");
+    
+    // Initialize hardware stubs
+    led_driver.begin();
+    switch_driver.begin();
+    
+    // Initialize MIDI transport
+    midi_transport.begin();
+    
+    // Initialize controller
+    controller.begin();
+    
+    // Create MIDI task on core 0 (high priority)
+    xTaskCreatePinnedToCore(
+        midi_task,
+        "midi_task",
+        4096,
+        NULL,
+        3,
+        &midi_task_handle,
+        0
+    );
+    
+    Serial.println("[INIT] All systems ready");
+    Serial.println("=============================");
+}
+
+void loop() {
+    // Controller task runs on core 1 (main Arduino loop)
+    controller.update();
+    delay(10);  // 10ms loop period
+}