tell_client: restore "No Pin in Gripper" detection on empty-gripper mount

Commit 071b4ab made mount() return SUCCESS as soon as it saw the intermediate
TELL "state"/Busy event, before the later "Gripper detection" event is read,
so an empty-gripper mount completed silently with no MountingFailed/pop-up.

check_command_ok blocks (wait_not_busy) until the mount sequence finishes, so
after it returns the robot's own record is authoritative: if get_mounted_sample()
is None the gripper was empty -> return NO_PIN_IN_GRIPPER, which the mounting
service maps to MountingFailed("No Pin in Gripper"). Covers manual and automation.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/aare/devices/tell_client.py

@@ -293,6 +293,15 @@ class TellClient:
                         timeout=wait_timeout, msg=f"Mount {segment}{puck}-{sample}: "
                     )
                     logger.info(f"Check command okay response: {msg}")
+                    # check_command_ok blocks (wait_not_busy) until the whole
+                    # mount sequence has finished, so the gripper-detection event
+                    # we observed as an intermediate "state"/Busy event is now
+                    # resolved. The robot's own record is authoritative: if it
+                    # reports nothing mounted, the gripper was empty (no pin),
+                    # which we must surface rather than reporting success.
+                    if self.get_mounted_sample() is None:
+                        logger.warning("Mount command completed but robot reports no sample mounted")
+                        return TellEventValueEnum.NO_PIN_IN_GRIPPER
                     return TellEventValueEnum.SUCCESS
                 elif (
                         event == TellEventTypeEnum.GIPPER_DETECTION.value