Fix NameError crash: current_time not defined on first tracking iteration

webcam rate-limiting used current_time before it was assigned on the
first loop iteration after START. Set current_time = start_time at
top of every loop iteration.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

teleop/teleop_hand_and_arm.py

@@ -471,6 +471,7 @@ if __name__ == '__main__':
         # main loop. robot start to follow VR user's motion
         while not STOP:
             start_time = time.time()
+            current_time = start_time  # Available everywhere in loop body
 
             # handle arm reset request
             if RESET_ARMS: