revert(x3): remove white pre-flash and CDI border attempt

Reverts bc62d882 and 509adada. The pre-flash added an extra full-sync
pass that made the black border artifact visibly larger. The CDI 0xA9
change had no effect on the border. Both are reverted while the true
cause of the x3 border is investigated.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/activities/boot_sleep/SleepActivity.cpp

@@ -4,7 +4,6 @@
 #include <Epub/converters/PngToFramebufferConverter.h>
 #include <FsHelpers.h>
 #include <GfxRenderer.h>
-#include <HalGPIO.h>
 #include <HalStorage.h>
 #include <I18n.h>
 #include <PNGdec.h>
@@ -358,19 +357,6 @@ void SleepActivity::onEnter() {
   if (SETTINGS.sleepScreen != CrossPointSettings::SLEEP_SCREEN_MODE::OVERLAY) {
     GUI.drawPopup(renderer, tr(STR_ENTERING_SLEEP));
   }
-  // X3 panels: flash white before rendering the sleep image so any ghosting from the reader
-  // page is fully cleared. The full sync triggered by requestResync drives the panel to a
-  // clean white state; the sleep screen is then drawn on top without residual ghost content.
-  // Skipped for OVERLAY (frame buffer must stay intact) and BLANK (already renders white).
-  const bool needsX3PreFlash = gpio.deviceIsX3() &&
-                               SETTINGS.sleepScreen != CrossPointSettings::SLEEP_SCREEN_MODE::OVERLAY &&
-                               SETTINGS.sleepScreen != CrossPointSettings::SLEEP_SCREEN_MODE::BLANK;
-  if (needsX3PreFlash) {
-    renderer.clearScreen();
-    display.requestResync(1);
-    renderer.displayBuffer(HalDisplay::HALF_REFRESH);
-  }
-
   switch (SETTINGS.sleepScreen) {
     case (CrossPointSettings::SLEEP_SCREEN_MODE::BLANK):
       return renderBlankSleepScreen();