Revert "USB serial logs now flow on cold+warm boot without jiggle (#2034)"

This reverts commit c539c11a74.

src/main.cpp

@@ -233,21 +233,6 @@ void setup() {
       esp_ota_mark_app_valid_cancel_rollback();
     }
   }
-#ifdef ENABLE_SERIAL_LOG
-  // Earliest possible Serial setup. The 250 ms stall before begin() lets the
-  // USB Serial/JTAG peripheral finish power-on and lets the host complete USB
-  // enumeration before we touch the CDC state — otherwise cold boot races
-  // and the host has to be physically replugged for logs to flow. Warm reboot
-  // worked without the delay because USB was already enumerated.
-  //
-  // setTxTimeoutMs(0) makes writes non-blocking — the HWCDC TX FIFO drops
-  // bytes harmlessly if the host isn't actively draining, instead of blocking
-  // for the default 250 ms per write and chaining into a firmware hang.
-  delay(250);
-  Serial.begin(115200);
-  logSerial.setTxTimeoutMs(0);
-#endif
-
   HalSystem::begin();
   gpio.begin();
   powerManager.begin();
@@ -264,6 +249,16 @@ void setup() {
     return;
   }
 
+#ifdef ENABLE_SERIAL_LOG
+  if (gpio.isUsbConnected()) {
+    Serial.begin(115200);
+    const unsigned long start = millis();
+    while (!Serial && (millis() - start) < 500) {
+      delay(10);
+    }
+  }
+#endif
+
   LOG_INF("MAIN", "Hardware detect: %s", gpio.deviceIsX3() ? "X3" : "X4");
   LOG_DBG("MAIN", "Wakeup reason: %d, millis=%lu, rawPowerPin=%d", static_cast<int>(wakeupReason), millis(),
           digitalRead(InputManager::POWER_BUTTON_PIN) == LOW);