Add retry logic for motion commands with 1-second timeout

- Wait up to 1 second for 'ok' response after sending G-code
- Automatically resend command if no response received
- Retries forever until 'ok' is received
- Prevents silent hang if response is missed

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

modules/core/pattern_manager.py

@@ -371,25 +371,37 @@ class MotionControlThread:
         state.machine_y = new_y_abs
 
     def _send_grbl_coordinates_sync(self, x: float, y: float, speed: int = 600, timeout: int = 2, home: bool = False):
-        """Synchronous version of send_grbl_coordinates for motion thread."""
-        logger.debug(f"Motion thread sending G-code: X{x} Y{y} at F{speed}")
+        """Synchronous version of send_grbl_coordinates for motion thread.
 
-        # Track overall attempt time
-        overall_start_time = time.time()
+        Sends coordinate and waits for 'ok'. If no 'ok' received within 1 second,
+        resends the command. Retries forever until 'ok' is received.
+        """
+        gcode = f"$J=G91 G21 Y{y} F{speed}" if home else f"G1 G53 X{x} Y{y} F{speed}"
+        retry_count = 0
 
         while True:
             try:
-                gcode = f"$J=G91 G21 Y{y} F{speed}" if home else f"G1 G53 X{x} Y{y} F{speed}"
+                # Check if stop was requested
+                if state.stop_requested:
+                    logger.debug("Motion thread: Stop requested, aborting send")
+                    return False
+
+                logger.debug(f"Motion thread sending G-code: {gcode}")
                 state.conn.send(gcode + "\n")
-                logger.debug(f"Motion thread sent command: {gcode}")
 
+                # Wait for 'ok' response with 1 second timeout
                 start_time = time.time()
-                while True:
+                while time.time() - start_time < 1.0:
                     response = state.conn.readline()
-                    logger.debug(f"Motion thread response: {response}")
-                    if response.lower() == "ok":
-                        logger.debug("Motion thread: Command execution confirmed.")
-                        return
+                    if response:
+                        logger.debug(f"Motion thread response: {response}")
+                        if response.lower() == "ok":
+                            logger.debug("Motion thread: Command execution confirmed.")
+                            return True
+
+                # No 'ok' received within timeout, will retry
+                retry_count += 1
+                logger.warning(f"Motion thread: No 'ok' received for {gcode}, resending... (attempt {retry_count})")
 
             except Exception as e:
                 error_str = str(e)
@@ -404,8 +416,11 @@ class MotionControlThread:
                     logger.info("Connection marked as disconnected due to device error")
                     return False
 
-            logger.warning(f"Motion thread: No 'ok' received for X{x} Y{y}, speed {speed}. Retrying...")
-            time.sleep(0.1)
+                retry_count += 1
+                logger.warning(f"Motion thread: Exception occurred, retrying... (attempt {retry_count})")
+
+            # Wait 1 second before resending
+            time.sleep(1.0)
 
 # Global motion control thread instance
 motion_controller = MotionControlThread()