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>

CHANGELOG.md

@@ -30,6 +30,7 @@
     - `/status` now publishes `pss_prohibited`/`pss_alarm`; the GUI blocks manual mount/unmount and the automation Run button immediately (with a pop-up) when the hutch door is open, instead of letting the robot fail to move server-side.
     - Centralised the per-action precondition checks (ring current, safety shutter, hutch door) into one combined "continue?" dialog used by all data-collection buttons (Evaluate grid, X-ray centering, Run screening/rotation/fluorescence, simple rotation), with a session-global "Don't ask me again for 1 hour" snooze.
     - Live automation now pauses and auto-resumes when the beam, experiment shutter, hutch door or robot (TELL) are not ready (with Continue-now / Stop overrides), gated by a "Pause on bad conditions" checkbox (default on) that replaces the dead `CHECK_ENABLED` constant.
+    - Restored "No Pin in Gripper" detection: a mount that returns on the intermediate TELL "Busy" state event now verifies the robot's `get_mounted_sample()` after the command completes, so an empty-gripper mount surfaces `MountingFailed` (and the GUI pop-up) instead of silently reporting success.
 
 ## 0.3.1 (2026-04-29)
 - **DAQ/Server**:

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

tests/unit/devices/test_tell_client.py

@@ -52,6 +52,8 @@ def test_mount_state_event_succeeds_when_command_completes(
         "id": 3017907,
     }
     client = TellClient(mock_beamline, backend=mock_backend)
+    # Robot reports the requested sample as mounted -> genuine success.
+    client.get_mounted_sample = lambda: _mount_address()
 
     result = client.mount(_mount_address(), wait=True)
 
@@ -59,6 +61,27 @@ def test_mount_state_event_succeeds_when_command_completes(
     mock_backend.get_result.assert_called()  # check_command_ok consulted the result
 
 
+def test_mount_state_event_reports_no_pin_when_nothing_mounted(
+    mock_beamline, mock_backend
+):
+    """If the command completes but the robot reports nothing mounted, the
+    gripper was empty: mount() must return NO_PIN_IN_GRIPPER (so the service
+    raises MountingFailed) rather than reporting success."""
+    mock_backend.wait_events.return_value = ("state", "Busy")
+    mock_backend.get_result.return_value = {
+        "status": "completed",
+        "return": "A39",
+        "exception": None,
+        "id": 3017907,
+    }
+    client = TellClient(mock_beamline, backend=mock_backend)
+    client.get_mounted_sample = lambda: None
+
+    result = client.mount(_mount_address(), wait=True)
+
+    assert result == TellEventValueEnum.NO_PIN_IN_GRIPPER
+
+
 def test_mount_state_event_raises_when_command_not_completed(
     mock_beamline, mock_backend
 ):