Auto-align: level the sample on the DC bias levels from the camera window

The operator frames a good spot, confirms the two DC levels the detector
reads there, and the rig then measures its own tilt: step 1.5 mm either side
on X and then on Y, and tilt the platform until those levels come back.  The
correction that fixes an offset point is the correction that levels the whole
travel — height error and tilt effect are both proportional to the offset —
so the procedure ends by applying it and leaving it applied.

Both directions are measured from the same starting tilt and averaged, which
makes their disagreement a flatness read-out rather than something averaged
away silently.

core/auto_align.py holds the geometry and the search, Qt-free.  The three
T-axes' azimuths are the whole geometry: T1 lies along +X so it alone tilts
along X, and T0/T2 move as an equal-and-opposite pair to tilt along Y without
touching X (tilt_response derives that, and the tests pin it — an axis map
that drifts would still converge, on the wrong axis).  The search is a secant
null on the split-detector difference: probe once to learn what a microstep
is worth, sign included, then step at the null.  It refuses to servo on a
scope that has not re-triggered, escalates a probe that reads as no response
before calling an axis dead, and stops at a per-axis travel limit.

gui/align_bridge.py runs it on a worker thread; stopping is a threading.Event
rather than a queued command, because the worker is inside a long handler for
the whole run.  The camera window carries the button and the progress window,
and locks the scan panel and the jog pads while a run owns the stage.

Adds immediate MEAN measurements and an acquisition count to the scope
driver, and read_bias_mv to core/scope_inspect — the one scalar the
inspection state was missing.

KNOWN_ISSUES.md records what only the rig can settle: the probe step, the
travel limit, the hold current, and whether the piston the X phase applies
alongside its tilt matters.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

tests/test_smoke_apps.py

@@ -38,6 +38,51 @@ def test_sc3_aui_main_window(qapp):
         _pump(qapp)
 
 
+def test_camera_window_without_hardware_is_a_plain_viewer(qapp):
+    """No stage, no scope, no auto-align button to press."""
+    import sc3_aui_app
+    win = sc3_aui_app.CameraWindow()
+    _pump(qapp)
+    try:
+        assert not win.uc480_auto_align_btn.isVisible()
+    finally:
+        win.deleteLater()
+        _pump(qapp)
+
+
+def test_camera_window_auto_align_needs_every_device(qapp):
+    """The button appears once the three devices exist, and says which one is
+    missing rather than starting and failing on the rig."""
+    import sc3_aui_app
+    from gui.qt_t3r import QtT3RAdapter
+    win = sc3_aui_app.CameraWindow(QtT3RAdapter(), sc3_aui_app.BBD202Worker(),
+                                   sc3_aui_app.OscopeWorker())
+    _pump(qapp)
+    try:
+        assert win.uc480_auto_align_btn.isVisibleTo(win)
+        assert "oscilloscope" in win._align_prerequisite_problem()
+    finally:
+        win.deleteLater()
+        _pump(qapp)
+
+
+def test_auto_align_window_logs_a_result(qapp):
+    import sc3_aui_app
+    from core.auto_align import AlignResult, Reading
+    win = sc3_aui_app.AutoAlignWindow()
+    _pump(qapp)
+    try:
+        reference = Reading(400.0, 400.0)
+        win.set_reference(reference)
+        win.on_reading(Reading(403.0, 397.0))
+        win.on_finished(AlignResult(reference=reference, final=reference))
+        assert "Reference" in win.log.toPlainText()
+        assert win.close_btn.isEnabled()
+    finally:
+        win.deleteLater()
+        _pump(qapp)
+
+
 def test_sras_viewer_window(qapp):
     import sras_viewer
     win = sras_viewer.SrasViewerWindow()