fix(damiao): make is_calibrated a plain property, not cached

`is_calibrated` was a `@cached_property`, so it froze at its first-read
value and never reflected later changes to `self.calibration` (set by
connect/calibrate/load). This caused the OpenArm teleop to re-run
calibration even when a calibration file existed, and to skip
`set_zero_position()` after a fresh calibration.

Switch to `@property` (matching the MotorsBus base contract and the
Feetech/SO-100 buses) and drop the now-unused `functools.cached_property`
import.

Co-authored-by: Cursor <cursoragent@cursor.com>

src/lerobot/motors/damiao/damiao.py

@@ -20,7 +20,6 @@ import logging
 import time
 from contextlib import contextmanager
 from copy import deepcopy
-from functools import cached_property
 from typing import TYPE_CHECKING, Any, TypedDict
 
 from lerobot.utils.decorators import check_if_already_connected, check_if_not_connected
@@ -854,7 +853,7 @@ class DamiaoMotorsBus(MotorsBusBase):
         else:
             raise ValueError(f"Motor {motor_obj} doesn't have a valid recv_id (None).")
 
-    @cached_property
+    @property
     def is_calibrated(self) -> bool:
         """Check if motors are calibrated."""
         return bool(self.calibration)