fix: remove grab_set() to allow main window interaction

UART Monitor window was modal (grab_set) preventing main window
from being used while the UART window is open. Remove grab_set
to make it modeless.

src/gui/widgets.py

@@ -800,9 +800,6 @@ class UartMonitorWindow(ctk.CTkToplevel):
         self.minsize(480, 360)
         self.protocol("WM_DELETE_WINDOW", self._on_close)
 
-        # Defer grab_set until window is viewable (avoids "window not viewable" error)
-        self.after(50, self._do_grab)
-
         self._port = port
         self._baudrate = baudrate
         self._monitor: UartMonitor | None = None
@@ -814,16 +811,9 @@ class UartMonitorWindow(ctk.CTkToplevel):
         self._build_log_area()
         self._build_status_bar()
 
-        # Try to open serial port after window is drawn
+       # Try to open serial port after window is drawn
         self.after(100, self._try_open)
 
-    def _do_grab(self) -> None:
-        """Acquire grab once window is viewable."""
-        try:
-            self.grab_set()
-        except Exception:
-            pass  # Window may have been destroyed already
-
     # ── Title Bar ──────────────────────────────────────────────
 
     def _build_title_bar(self) -> None: