refactor(nidaq): replace placeholder signals with DynamicSignal statistic groups

tests/tests_devices/test_nidaq.py

@@ -182,3 +182,29 @@ def test_on_complete(mock_nidaq, scan_info_mock):
     dev.stop()
     status.wait(timeout=5)
     assert status.done is True
+
+
+########## DynamicSignal statistic groups ##########
+
+from ophyd import Kind
+from ophyd_devices.utils.bec_signals import DynamicSignal
+
+
+def test_statistic_groups_and_omitted_epics(mock_nidaq):
+    """Groups own the unified namespace; EPICS scalars are silent data sources.
+
+    DynamicSignal is deliberate (per the NIDAQ maintainers, the active channel
+    set cannot be predicted upfront): channel names are validated, batch
+    completeness is not.
+    """
+    dev = mock_nidaq
+    assert isinstance(dev.mean, DynamicSignal)
+    assert dev.mean.strict_signal_validation is False
+    assert dev.mean.name == "nidaq_mean"
+    assert dev.max.name == "nidaq_max"
+    assert dev.std_dev.name == "nidaq_std_dev"
+    assert dev.stream.name == "nidaq_stream"
+    # EPICS scalars demoted: no longer in the readout namespace
+    assert dev.ai0.kind == Kind.omitted
+    assert dev.enc_epics.kind == Kind.omitted
+    assert "nidaq_ai0" not in dev.read()