Add VP connection timestamp tracking for LED status indicator

Add last_data_time_shared timestamp updated in all three Vuer event
handlers (CAMERA_MOVE, HAND_MOVE, CONTROLLER_MOVE). Exposes
last_data_time property for the main teleop loop to detect VP
connection freshness (connected if data received within 1 second).

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

src/televuer/televuer.py

@@ -6,6 +6,7 @@ import asyncio
 import threading
 import cv2
 import os
+import time as _time
 from pathlib import Path
 from typing import Literal
 
@@ -138,6 +139,8 @@ class TeleVuer:
         
         self.vuer.spawn(start=False)(fn)
 
+        self.last_data_time_shared = Value('d', 0.0, lock=True)
+
         self.head_pose_shared = Array('d', 16, lock=True)
         self.left_arm_pose_shared = Array('d', 16, lock=True)
         self.right_arm_pose_shared = Array('d', 16, lock=True)
@@ -225,6 +228,8 @@ class TeleVuer:
         try:
             with self.head_pose_shared.get_lock():
                 self.head_pose_shared[:] = event.value["camera"]["matrix"]
+            with self.last_data_time_shared.get_lock():
+                self.last_data_time_shared.value = _time.time()
         except:
             pass
 
@@ -264,6 +269,8 @@ class TeleVuer:
 
             extract_controllers(left_controller, "left")
             extract_controllers(right_controller, "right")
+            with self.last_data_time_shared.get_lock():
+                self.last_data_time_shared.value = _time.time()
         except:
             pass
 
@@ -310,10 +317,12 @@ class TeleVuer:
             extract_hand_poses(right_hand_data, self.right_arm_pose_shared, self.right_hand_position_shared, self.right_hand_orientation_shared)
             extract_hands(left_hand, "left")
             extract_hands(right_hand, "right")
+            with self.last_data_time_shared.get_lock():
+                self.last_data_time_shared.value = _time.time()
 
         except:
             pass
-    
+
     ## immersive MODE
     async def main_image_binocular_zmq(self, session):
         if self.use_hand_tracking:
@@ -679,6 +688,12 @@ class TeleVuer:
             await asyncio.sleep(1.0 / self.display_fps)
 
     # ==================== common data ====================
+    @property
+    def last_data_time(self):
+        """float, timestamp of last VP data received (0.0 = never)."""
+        with self.last_data_time_shared.get_lock():
+            return self.last_data_time_shared.value
+
     @property
     def head_pose(self):
         """np.ndarray, shape (4, 4), head SE(3) pose matrix from Vuer (basis OpenXR Convention)."""