Add SysEx handling for Launchpad X Programmer mode

- Parse all SysEx CIN types (start, continue, end)
- Reassemble multi-packet SysEx messages
- Handle layout select (Programmer mode = 0x7F)
- Handle Programmer/Live mode switch

include/app_task.h

@@ -29,6 +29,14 @@ private:
     PadMapping pad_mapping[NUM_PADS];
     bool last_switch_state[NUM_PADS];
     
+    // SysEx reassembly buffer
+    static const uint8_t SYSEX_MAX_LEN = 64;
+    uint8_t sysex_buffer[SYSEX_MAX_LEN];
+    uint8_t sysex_len = 0;
+    bool sysex_active = false;
+    
     void process_switch_event(uint8_t switch_id, bool pressed);
     void run_palette_test();
+    void handle_sysex(const uint8_t* data, uint8_t len);
+    void process_sysex_packet(const uint8_t* packet, uint8_t cin);
 };