Required for uint16_t, Serial, millis() etc. when compiling outside the .ino (Arduino IDE auto-includes Arduino.h for .ino files but not for standalone .cpp files).
Gfx / GfxSprite types: - TFT_eSPI path: zero-cost typedefs to TFT_eSPI / TFT_eSprite - Arduino_GFX path: adapter classes with TFT_eSPI-compatible API DisplayDriverGFX.cpp compiles to nothing on TFT_eSPI targets. GfxSprite on Arduino_GFX uses direct-draw (no offscreen buffer yet).
