move requestResync to HAL

lib/hal/HalDisplay.h

@@ -36,9 +36,6 @@ class HalDisplay {
 
   void displayBuffer(RefreshMode mode = RefreshMode::FAST_REFRESH, bool turnOffScreen = false);
   void refreshDisplay(RefreshMode mode = RefreshMode::FAST_REFRESH, bool turnOffScreen = false);
-  // Hint the display driver to perform a one-shot full resync on next update.
-  // Optional settle passes are used by X3 only.
-  void requestResync(uint8_t settlePasses = 0);
 
   // Power management
   void deepSleep();
@@ -61,4 +58,5 @@ class HalDisplay {
 
  private:
   EInkDisplay einkDisplay;
+  bool lastBufferWasGray = false;
 };