🐛 fix: Step 4 boot wait uses UART window monitor data, not just main monitor

Root cause: When UART window is open, self._uart_monitor is None
(the window creates its own UartMonitor). Step 4 boot wait loop
only checked self._uart_monitor.latest_info → always saw empty data
→ fell through to IP scanning even though UART had detected the IP.

Fix:
- UartMonitorWindow.get_latest_info() exposes parsed BootInfo
- Step 4 checks both: self._uart_monitor first, then UART window
- Null guard on info before accessing .ip_address

src/gui/main_window.py

@@ -1144,15 +1144,23 @@ class MainWindow(ctk.CTk):
 
         # Wait for board to boot — UART if available, else config delay
         boot_delay = self._config.boot_wait_delay
-        uart_alive = (self._uart_monitor is not None
-                      and self._uart_monitor.is_running())
+        # Check both main monitor and UART window monitor
+        uart_alive = False
+        _uart_src = None  # source of latest_info
+        if self._uart_monitor and self._uart_monitor.is_running():
+            uart_alive = True
+            _uart_src = self._uart_monitor
+        elif (self._uart_window and self._uart_window.winfo_exists()
+              and self._uart_window.is_monitoring):
+            uart_alive = True
+            _uart_src = self._uart_window
         discovered_ip: str = ""
-        if uart_alive:
+        if uart_alive and _uart_src:
             self._log_message(f"  ⏳ Waiting for UART boot signal (max {boot_delay}s)...")
             elapsed = 0.0
             while elapsed < boot_delay:
-                info = self._uart_monitor.latest_info
-                if info.ip_address or info.version:
+                info = _uart_src.latest_info if hasattr(_uart_src, 'latest_info') else _uart_src.get_latest_info()
+                if info and (info.ip_address or info.version):
                     self._log_message(
                         f"  ✓ Boot detected after {elapsed:.1f}s"
                         f" (IP={info.ip_address}, Ver={info.version})"