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>

gui/jog_panel.py

@@ -15,13 +15,13 @@ already does it.
 from __future__ import annotations
 
 from PyQt6.QtCore import Qt, QTimer
-from PyQt6.QtGui import QFont
 from PyQt6.QtWidgets import (
     QCheckBox, QComboBox, QDoubleSpinBox, QFrame, QGridLayout, QGroupBox,
     QLabel, QPushButton, QSpinBox,
 )
 
 import hardware.t3r_protocol as proto
+from gui.widgets import mono_font
 from hardware.t3r_driver import T3RDriver
 
 # BBD202 jog defaults, shared with the main window's worker.
@@ -44,13 +44,6 @@ BBD_JOG_REPEAT_MS = 200
 BBD_VELOCITY_DEBOUNCE_MS = 300
 
 
-def _mono(size: int = 11) -> QFont:
-    f = QFont("Menlo")
-    f.setStyleHint(QFont.StyleHint.Monospace)
-    f.setPointSize(size)
-    return f
-
-
 def _hline() -> QFrame:
     line = QFrame()
     line.setFrameShape(QFrame.Shape.HLine)
@@ -157,7 +150,7 @@ class T3RJogPanel(QGroupBox):
             self._micro_combos[ch] = combo
 
             pos_lbl = QLabel("—")
-            pos_lbl.setFont(_mono(11))
+            pos_lbl.setFont(mono_font(11))
             pos_lbl.setMinimumWidth(76)
             pos_lbl.setAlignment(Qt.AlignmentFlag.AlignRight | Qt.AlignmentFlag.AlignVCenter)
             grid.addWidget(pos_lbl, row, 4)
@@ -280,11 +273,11 @@ class BBDJogPanel(QGroupBox):
 
         grid.addWidget(QLabel("X"), row, 0)
         self.x_pos_lbl = QLabel("---.---")
-        self.x_pos_lbl.setFont(_mono(11))
+        self.x_pos_lbl.setFont(mono_font(11))
         grid.addWidget(self.x_pos_lbl, row, 1)
         grid.addWidget(QLabel("Y"), row, 2)
         self.y_pos_lbl = QLabel("---.---")
-        self.y_pos_lbl.setFont(_mono(11))
+        self.y_pos_lbl.setFont(mono_font(11))
         grid.addWidget(self.y_pos_lbl, row, 3)
         row += 1