fix(display): stop SH1106 boot crash when the boot-time probe fails

The upstream merge switched SH1106Display::begin() to probe-then-init.
On the T-Beam S3 Supreme the OLED bus can NAK a cold address probe, so
begin() bailed before display.begin() ever ran, and UITask::begin()'s
unconditional turnOn() then drove Adafruit_GrayOLED with a null bus
device: bogus gpio_set_level(227) followed by a LoadProhibited boot loop.

Restore the proven S3 Supreme bring-up order (Adafruit init with reset
sequence first, then settle the bus and verify), and track begin()
success so turnOn/turnOff/clear are safe no-ops when the display never
initialised - a failed or absent display now boots headless instead of
crash-looping.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

src/helpers/ui/SH1106Display.cpp

@@ -23,29 +23,39 @@ ColorVal UIColor::corp_blue = SH110X_WHITE;
 bool SH1106Display::begin()
 {
 #if defined(ESP32) && defined(TBEAM_SUPREME_SX1262) && defined(PIN_BOARD_SDA) && defined(PIN_BOARD_SCL)
+  // The S3 Supreme OLED bus NAKs cold address probes on some boards, so run the
+  // Adafruit init (with its reset sequence) first, then settle the bus before
+  // verifying the display responds.
+  _began = display.begin(DISPLAY_ADDRESS, true);
   Wire.begin(PIN_BOARD_SDA, PIN_BOARD_SCL);
   Wire.setClock(100000);
-#endif
+  _began = _began && i2c_probe(Wire, DISPLAY_ADDRESS);
+#else
   // Wire must already be initialised by board.begin() before this is called.
   // Boards with non-standard SH1106 addresses should define DISPLAY_ADDRESS
   // in their variant/platformio configuration.
-  return i2c_probe(Wire, DISPLAY_ADDRESS) && display.begin(DISPLAY_ADDRESS, true);
+  _began = i2c_probe(Wire, DISPLAY_ADDRESS) && display.begin(DISPLAY_ADDRESS, true);
+#endif
+  return _began;
 }
 
 void SH1106Display::turnOn()
 {
+  if (!_began) return;  // display.begin() never ran; oled_command would crash on a null bus device
   display.oled_command(SH110X_DISPLAYON);
   _isOn = true;
 }
 
 void SH1106Display::turnOff()
 {
+  if (!_began) return;
   display.oled_command(SH110X_DISPLAYOFF);
   _isOn = false;
 }
 
 void SH1106Display::clear()
 {
+  if (!_began) return;
   display.clearDisplay();
   display.display();
 }

src/helpers/ui/SH1106Display.h

@@ -18,12 +18,13 @@ class SH1106Display : public DisplayDriver
 {
   Adafruit_SH1106G display;
   bool _isOn;
+  bool _began;
   uint8_t _color;
 
   bool i2c_probe(TwoWire &wire, uint8_t addr);
 
 public:
-  SH1106Display() : DisplayDriver(128, 64), display(128, 64, &Wire, PIN_OLED_RESET) { _isOn = false; }
+  SH1106Display() : DisplayDriver(128, 64), display(128, 64, &Wire, PIN_OLED_RESET) { _isOn = false; _began = false; }
   bool begin();
 
   bool isOn() override { return _isOn; }