fix(t5s3-epaper): 40MHz octal PSRAM; guard EInk init; esp32s3 sw-atomic shim (#11062)

- t5s3-epaper: the board's 3.3V octal (AP_3v3) PSRAM is unreliable at the qio_opi
  default of 80MHz (Total PSRAM reads 0, display dead / boot-loop); clock it at 40MHz.
- EInkParallelDisplay: skip EInk init and no-op display ops when the PSRAM framebuffer
  is unavailable, so the node boots headless instead of hard-faulting on a NULL buffer.
- src/platform/esp32: weak software __atomic_*_{1,2,4} so esp32s3 links on toolchains
  (e.g. macOS) that lack the sized libcalls GCC emits under -mdisable-hardware-atomics.

src/graphics/EInkParallelDisplay.cpp

@@ -77,12 +77,13 @@ EInkParallelDisplay::~EInkParallelDisplay()
 bool EInkParallelDisplay::connect()
 {
     LOG_INFO("Do EPD init");
+    int initRc = BBEP_SUCCESS;
     if (!epaper) {
         epaper = new FASTEPD;
 #if defined(T5_S3_EPAPER_PRO_V1)
-        epaper->initPanel(BB_PANEL_LILYGO_T5PRO, 28000000);
+        initRc = epaper->initPanel(BB_PANEL_LILYGO_T5PRO, 28000000);
 #elif defined(T5_S3_EPAPER_PRO_V2)
-        epaper->initPanel(BB_PANEL_LILYGO_T5PRO_V2, 28000000);
+        initRc = epaper->initPanel(BB_PANEL_LILYGO_T5PRO_V2, 28000000);
         // initialize all port 0 pins (0-7) as outputs / HIGH
         for (int i = 0; i < 8; i++) {
             epaper->ioPinMode(i, OUTPUT);
@@ -93,6 +94,16 @@ bool EInkParallelDisplay::connect()
 #endif
     }
 
+    // FastEPD allocates its framebuffer only from PSRAM; if PSRAM init failed the alloc returns
+    // NULL and initPanel() returns an error, so clearWhite() below would memset(NULL). Skip EInk
+    // bring-up but return true so OLEDDisplay still allocates its base buffer (base draw ops stay
+    // safe); displayReady stays false so the FastEPD push paths no-op -> node runs headless.
+    if (initRc != BBEP_SUCCESS || epaper->currentBuffer() == nullptr) {
+        LOG_ERROR("EPD framebuffer unavailable (initPanel rc=%d, PSRAM=%u); running headless", initRc,
+                  (unsigned)ESP.getPsramSize());
+        return true;
+    }
+
     // epaper->setRotation(rotation); // does not work, messes up width/height
     epaper->setMode(BB_MODE_1BPP);
     epaper->clearWhite();
@@ -103,6 +114,7 @@ bool EInkParallelDisplay::connect()
     resetGhostPixelTracking();
 #endif
 
+    displayReady = true;
     return true;
 }
 
@@ -187,6 +199,9 @@ void EInkParallelDisplay::asyncFullUpdateTask(void *pvParameters)
  */
 void EInkParallelDisplay::display(void)
 {
+    if (!displayReady) // no framebuffer (PSRAM absent / init failed) -> nothing to push
+        return;
+
     const uint16_t w = this->displayWidth;
     const uint16_t h = this->displayHeight;
 
@@ -400,6 +415,9 @@ void EInkParallelDisplay::resetGhostPixelTracking()
  */
 bool EInkParallelDisplay::forceDisplay(uint32_t msecLimit)
 {
+    if (!displayReady)
+        return false;
+
     uint32_t now = millis();
     if (lastDrawMsec == 0 || (now - lastDrawMsec) > msecLimit) {
         display();
@@ -410,6 +428,8 @@ bool EInkParallelDisplay::forceDisplay(uint32_t msecLimit)
 
 void EInkParallelDisplay::endUpdate()
 {
+    if (!displayReady)
+        return;
     {
         // ensure any async full update is started/completed
         if (asyncFullRunning.load()) {

src/graphics/EInkParallelDisplay.h

@@ -40,6 +40,9 @@ class EInkParallelDisplay : public OLEDDisplay
     uint32_t lastDrawMsec = 0;
     FASTEPD *epaper;
 
+    // Set only when connect() fully succeeds; framebuffer-touching methods no-op while false.
+    bool displayReady = false;
+
   private:
     // Async full-refresh support
     std::atomic<bool> asyncFullRunning{false};