fix: 修改 RealManAdapter 中对机械臂的引用，确保正确获取关节状态

xr_rm_teleop/xr_rm_teleop/realman_adapter.py

@@ -237,9 +237,9 @@ class RealManAdapter:
             )
 
     def read_joint_state(self) -> JointStateSnapshot:
-        self._require_arm()
+        arm = self._require_arm()
         started_at = time.monotonic()
-        result = self._arm.rm_get_joint_degree()
+        result = arm.rm_get_joint_degree()
         finished_at = time.monotonic()
         if not isinstance(result, tuple) or len(result) != 2:
             raise RuntimeError(
@@ -256,10 +256,10 @@ class RealManAdapter:
         )
 
     def send_joint_target(self, joints: list[float], follow: bool) -> None:
-        self._require_arm()
+        arm = self._require_arm()
         if len(joints) != 7 or not all(math.isfinite(value) for value in joints):
             raise ValueError("joint target must contain 7 finite values")
-        ret = self._arm.rm_movej_canfd(
+        ret = arm.rm_movej_canfd(
             [math.degrees(value) for value in joints],
             follow,
             0,
@@ -315,9 +315,10 @@ class RealManAdapter:
             self._arm = None
             self._realtime_callback = None
 
-    def _require_arm(self) -> None:
+    def _require_arm(self) -> Any:
         if self._arm is None:
             raise RuntimeError("睿尔曼机械臂尚未连接")
+        return self._arm
 
     def _on_realtime_arm_state(self, data: Any) -> None:
         if not self._accept_realtime_feedback:
@@ -457,11 +458,11 @@ class RealManAdapter:
             self._try_call("rm_set_joint_max_acc", joint_index, self._joint_max_acc)
 
     def move_to_initial_pose(self) -> None:
-        self._require_arm()
+        arm = self._require_arm()
         if self._initial_joint_pose is None:
             raise RuntimeError("启用初始位姿移动时必须配置 initial_joint_pose")
 
-        ret = self._arm.rm_movej(
+        ret = arm.rm_movej(
             self._initial_joint_pose,
             self._init_move_speed,
             0,