docs(devices): document the laser delay phase path, runtime settings and PV failures

superxas_bec/devices/laser_delay.py

@@ -435,7 +435,8 @@ class LaserDelay(PSIDeviceBase, PositionerBase):
         doc="Stored (unwrapped) phase shifter delay in ns",
     )
 
-    # Tunable constants (deviceConfig; runtime changes via set_device_config apply to the next move)
+    # Tunable constants (deviceConfig). Runtime changes (dev.laser_delay.step_sleep.set(0.05)) apply
+    # to the next move.
     rf_period = Cpt(
         CheckedSignal, value=2.0, kind=Kind.config, validator=_positive_number("rf_period")
     )
@@ -501,7 +502,7 @@ class LaserDelay(PSIDeviceBase, PositionerBase):
         self._phase_v1_pv = phase_v1_pv
         self._phase_v2_pv = phase_v2_pv
         self._move_lock = threading.RLock()  # guards _move_status and _move_stop
-        self._hw_lock = threading.Lock()  # held by the move task while it writes PVs
+        self._hw_lock = threading.Lock()  # held by the move task and by calibrate/set_calibration
         self._move_stop = threading.Event()  # one event per move, set to interrupt that move
         self._move_status: StatusBase | None = None
         super().__init__(