feat(wafer-map): add threshold legend overlay and scrollbar polish

- Add color legend (Low/In-range/High + Auto/Manual mode)
  as a floating overlay in WaferMapView
- Expose thresholdAuto on SessionController/SessionModel
  to drive the legend's Auto · / Manual · label
- Style ReadoutPanel scrollbar (always-visible, 8px thumb)
  and reserve 14px gap so cards don't overlap it

src/pygui/ISC/Tabs/WaferMapTab.qml

@@ -193,18 +193,42 @@ Item {
                 }
             }
 
-            // Readout panel — scrolls instead of clipping so the last card
+            // Readout panel — scrolls instead of clipping so no card is lost
-            // (Thresholds) is always reachable even if content outgrows
+            // if content outgrows the available height (e.g. once E-C delta
-            // the available height (e.g. once E-C delta rows appear).
+            // rows appear). Thresholds sits first so it's visible unscrolled.
             ScrollView {
+                id: readoutScroll
                 Layout.preferredWidth: Theme.rightRailWidth
                 Layout.fillHeight: true
                 clip: true
                 ScrollBar.horizontal.policy: ScrollBar.AlwaysOff
 
+                ScrollBar.vertical: ScrollBar {
+                    parent: readoutScroll
+                    anchors.top: readoutScroll.top
+                    anchors.right: readoutScroll.right
+                    anchors.bottom: readoutScroll.bottom
+                    anchors.leftMargin: 6
+                    policy: ScrollBar.AlwaysOn
+
+                    contentItem: Rectangle {
+                        implicitWidth: 8
+                        implicitHeight: 8
+                        radius: Theme.radiusSm
+                        color: Theme.trackBackground
+                    }
+
+                    background: Rectangle {
+                        implicitWidth: 8
+                        color: "transparent"
+                    }
+                }
+
                 ReadoutPanel {
                     id: readoutPanel
-                    width: parent.width
+                    // Reserve a gap before the always-visible scrollbar so
+                    // card content doesn't sit flush against it.
+                    width: readoutScroll.availableWidth - 14
                     hasThicknessData: waferView.hasThickness
                     onExportRequested: function(filePath, extra) {
                         waferView.exportImage(filePath, extra);

src/pygui/ISC/Tabs/components/ReadoutPanel.qml

@@ -5,10 +5,13 @@ import QtQuick.Layouts
 import ISC
 
 // ===== Readout Panel =====
-// Right-rail panel with three bento-tile sections: READOUT, DISPLAY,
+// Right-rail panel with three bento-tile sections: THRESHOLDS, DISPLAY,
-// THRESHOLDS. Uses the same PanelBox / SectionTitle / ReadoutStat /
+// READOUT. Thresholds comes first so Set Point/Margin/Auto are visible
-// PanelCheckBox / PanelSlider components as the Data tab's
+// without scrolling on first use. The whole panel scrolls as one column
-// ComparisonSidePanel, so both right rails share one visual language.
+// (see WaferMapTab.qml) when content outgrows the available height.
+// Uses the same PanelBox / SectionTitle / ReadoutStat / PanelCheckBox /
+// PanelSlider components as the Data tab's ComparisonSidePanel, so both
+// right rails share one visual language.
 ColumnLayout {
     id: root
     spacing: 6
@@ -47,63 +50,85 @@ ColumnLayout {
         }
     }
 
-    // ── READOUT ─────────────────────────────────────────────────────
+    // ── THRESHOLDS ──────────────────────────────────────────────────
     PanelBox {
         Layout.fillWidth: true
-        Layout.preferredHeight: readoutCol.implicitHeight + 24
+        Layout.preferredHeight: thresholdCard.implicitHeight + 24
 
         ColumnLayout {
-            id: readoutCol
+            id: thresholdCard
             anchors.fill: parent
             anchors.margins: 12
-            spacing: 8
+            spacing: 6
 
-            SectionTitle { text: "READOUT" }
+            SectionTitle { text: "THRESHOLDS" }
 
-            ReadoutStat {
+            Label {
-                label: "Min Temp"
+                text: "Set Point (°C)"
-                value: s.min !== undefined
+                color: Theme.bodyColor
-                    ? s.min + ((s.minIndex !== undefined && s.minIndex >= 0) ? "  #" + s.minIndex : "")
+                font.pixelSize: Theme.fontSm
-                    : "—"
-                valueColor: Theme.sensorLow
             }
-            ReadoutStat {
+            TextField {
-                label: "Max Temp"
+                id: spField
-                value: s.max !== undefined
+                Layout.fillWidth: true
-                    ? s.max + ((s.maxIndex !== undefined && s.maxIndex >= 0) ? "  #" + s.maxIndex : "")
+                text: "149.0"
-                    : "—"
+                font.pixelSize: Theme.fontSm
-                valueColor: Theme.sensorHigh
+                inputMethodHints: Qt.ImhFormattedNumbersOnly
+                color: Theme.fieldText
+                placeholderTextColor: Theme.fieldPlaceholder
+                selectedTextColor: Theme.fieldBackground
+                selectionColor: Theme.fieldText
+                background: Rectangle {
+                    radius: Theme.radiusXs
+                    color: Theme.fieldBackground
+                    border.width: spField.activeFocus ? Theme.borderStrong : Theme.borderThin
+                    border.color: spField.activeFocus ? Theme.fieldBorderFocus : Theme.fieldBorder
+                    Behavior on color {
+                        ColorAnimation { duration: Theme.durationFast }
+                    }
+                    Behavior on border.color {
+                        ColorAnimation { duration: Theme.durationFast }
+                    }
+                }
+                onEditingFinished: pushThresholds()
             }
-            ReadoutStat {
+
-                label: "Diff"
+            Label {
-                value: s.diff !== undefined ? s.diff : "—"
+                text: "Margin (±°C)"
-                valueColor: Theme.diffAccent
+                color: Theme.bodyColor
+                font.pixelSize: Theme.fontSm
             }
-            ReadoutStat {
+            TextField {
-                label: "Average"
+                id: mgField
-                value: s.avg !== undefined ? s.avg : "—"
+                Layout.fillWidth: true
+                text: "1.0"
+                font.pixelSize: Theme.fontSm
+                inputMethodHints: Qt.ImhFormattedNumbersOnly
+                color: Theme.fieldText
+                placeholderTextColor: Theme.fieldPlaceholder
+                selectedTextColor: Theme.fieldBackground
+                selectionColor: Theme.fieldText
+                background: Rectangle {
+                    radius: Theme.radiusXs
+                    color: Theme.fieldBackground
+                    border.width: mgField.activeFocus ? Theme.borderStrong : Theme.borderThin
+                    border.color: mgField.activeFocus ? Theme.fieldBorderFocus : Theme.fieldBorder
+                    Behavior on color {
+                        ColorAnimation { duration: Theme.durationFast }
+                    }
+                    Behavior on border.color {
+                        ColorAnimation { duration: Theme.durationFast }
+                    }
+                }
+                onEditingFinished: pushThresholds()
             }
-            ReadoutStat {
+
-                label: "Sigma (Σ)"
+            PanelCheckBox {
-                value: s.sigma !== undefined ? s.sigma : "—"
+                id: autoCheck
-            }
+                text: "Auto range  (mean ± 1σ)"
-            ReadoutStat {
+                checked: true
-                label: "3Σ Value"
+                font.pixelSize: Theme.fontSm
-                value: s.threeSigma !== undefined ? s.threeSigma : "—"
+                onCheckedChanged: pushThresholds()
-            }
-            ReadoutStat {
-                visible: s.ecMinDelta !== undefined
-                label: "E-C Δ Min"
-                value: s.ecMinDelta !== undefined
-                    ? s.ecMinDelta.toFixed(2) + " (#" + s.ecMinEdgeIndex + "→#" + s.ecMinCenterIndex + ")"
-                    : "—"
-            }
-            ReadoutStat {
-                visible: s.ecMaxDelta !== undefined
-                label: "E-C Δ Max"
-                value: s.ecMaxDelta !== undefined
-                    ? s.ecMaxDelta.toFixed(2) + " (#" + s.ecMaxEdgeIndex + "→#" + s.ecMaxCenterIndex + ")"
-                    : "—"
             }
         }
     }
@@ -203,85 +228,63 @@ ColumnLayout {
         }
     }
 
-    // ── THRESHOLDS ──────────────────────────────────────────────────
+    // ── READOUT ─────────────────────────────────────────────────────
     PanelBox {
         Layout.fillWidth: true
-        Layout.preferredHeight: thresholdCard.implicitHeight + 24
+        Layout.preferredHeight: readoutCol.implicitHeight + 24
 
         ColumnLayout {
-            id: thresholdCard
+            id: readoutCol
             anchors.fill: parent
             anchors.margins: 12
-            spacing: 6
+            spacing: 8
 
-            SectionTitle { text: "THRESHOLDS" }
+            SectionTitle { text: "READOUT" }
 
-            Label {
+            ReadoutStat {
-                text: "Set Point (°C)"
+                label: "Min Temp"
-                color: Theme.bodyColor
+                value: s.min !== undefined
-                font.pixelSize: Theme.fontSm
+                    ? s.min + ((s.minIndex !== undefined && s.minIndex >= 0) ? "  #" + s.minIndex : "")
+                    : "—"
+                valueColor: Theme.sensorLow
             }
-            TextField {
+            ReadoutStat {
-                id: spField
+                label: "Max Temp"
-                Layout.fillWidth: true
+                value: s.max !== undefined
-                text: "149.0"
+                    ? s.max + ((s.maxIndex !== undefined && s.maxIndex >= 0) ? "  #" + s.maxIndex : "")
-                font.pixelSize: Theme.fontSm
+                    : "—"
-                inputMethodHints: Qt.ImhFormattedNumbersOnly
+                valueColor: Theme.sensorHigh
-                color: Theme.fieldText
-                placeholderTextColor: Theme.fieldPlaceholder
-                selectedTextColor: Theme.fieldBackground
-                selectionColor: Theme.fieldText
-                background: Rectangle {
-                    radius: Theme.radiusXs
-                    color: Theme.fieldBackground
-                    border.width: spField.activeFocus ? Theme.borderStrong : Theme.borderThin
-                    border.color: spField.activeFocus ? Theme.fieldBorderFocus : Theme.fieldBorder
-                    Behavior on color {
-                        ColorAnimation { duration: Theme.durationFast }
-                    }
-                    Behavior on border.color {
-                        ColorAnimation { duration: Theme.durationFast }
-                    }
-                }
-                onEditingFinished: pushThresholds()
             }
-
+            ReadoutStat {
-            Label {
+                label: "Diff"
-                text: "Margin (±°C)"
+                value: s.diff !== undefined ? s.diff : "—"
-                color: Theme.bodyColor
+                valueColor: Theme.diffAccent
-                font.pixelSize: Theme.fontSm
             }
-            TextField {
+            ReadoutStat {
-                id: mgField
+                label: "Average"
-                Layout.fillWidth: true
+                value: s.avg !== undefined ? s.avg : "—"
-                text: "1.0"
-                font.pixelSize: Theme.fontSm
-                inputMethodHints: Qt.ImhFormattedNumbersOnly
-                color: Theme.fieldText
-                placeholderTextColor: Theme.fieldPlaceholder
-                selectedTextColor: Theme.fieldBackground
-                selectionColor: Theme.fieldText
-                background: Rectangle {
-                    radius: Theme.radiusXs
-                    color: Theme.fieldBackground
-                    border.width: mgField.activeFocus ? Theme.borderStrong : Theme.borderThin
-                    border.color: mgField.activeFocus ? Theme.fieldBorderFocus : Theme.fieldBorder
-                    Behavior on color {
-                        ColorAnimation { duration: Theme.durationFast }
-                    }
-                    Behavior on border.color {
-                        ColorAnimation { duration: Theme.durationFast }
-                    }
-                }
-                onEditingFinished: pushThresholds()
             }
-
+            ReadoutStat {
-            PanelCheckBox {
+                label: "Sigma (Σ)"
-                id: autoCheck
+                value: s.sigma !== undefined ? s.sigma : "—"
-                text: "Auto range  (mean ± 1σ)"
+            }
-                checked: true
+            ReadoutStat {
-                font.pixelSize: Theme.fontSm
+                label: "3Σ Value"
-                onCheckedChanged: pushThresholds()
+                value: s.threeSigma !== undefined ? s.threeSigma : "—"
+            }
+            ReadoutStat {
+                visible: s.ecMinDelta !== undefined
+                label: "E-C Δ Min"
+                value: s.ecMinDelta !== undefined
+                    ? s.ecMinDelta.toFixed(2) + " (#" + s.ecMinEdgeIndex + "→#" + s.ecMinCenterIndex + ")"
+                    : "—"
+            }
+            ReadoutStat {
+                visible: s.ecMaxDelta !== undefined
+                label: "E-C Δ Max"
+                value: s.ecMaxDelta !== undefined
+                    ? s.ecMaxDelta.toFixed(2) + " (#" + s.ecMaxEdgeIndex + "→#" + s.ecMaxCenterIndex + ")"
+                    : "—"
             }
         }
     }

src/pygui/ISC/Tabs/components/ReplaceSensorDialog.qml

@@ -5,6 +5,7 @@ import ISC
 
 Dialog {
     id: root
+    parent: Overlay.overlay
     title: "Sensor Override"
     modal: true
     standardButtons: Dialog.NoButton

src/pygui/ISC/Tabs/components/WaferMapView.qml

@@ -1,5 +1,6 @@
 import QtQuick
 import QtQuick.Controls
+import QtQuick.Layouts
 import ISC
 import ISC.Wafer
 
@@ -64,6 +65,64 @@ Item {
         id: replaceDialog
     }
 
+    // ── Threshold legend: what Low/In-range/High mean, and whether the
+    // band is auto-derived (frame mean ± 1σ) or the manual set point.
+    // Same computation in live and review, so no mode-specific text needed —
+    // the resolved values below just reflect whichever frame is current.
+    Rectangle {
+        id: thresholdLegend
+        visible: streamController.sensorValues.length > 0
+        anchors.right: parent.right
+        anchors.bottom: parent.bottom
+        anchors.margins: 10
+        radius: Theme.radiusSm
+        color: Theme.sidePanelBackground
+        opacity: 0.9
+        border.color: Theme.sideBorder
+        border.width: Theme.borderThin
+        implicitWidth: legendRow.implicitWidth + 20
+        implicitHeight: legendRow.implicitHeight + 12
+
+        RowLayout {
+            id: legendRow
+            anchors.centerIn: parent
+            spacing: 14
+
+            Row {
+                spacing: 10
+                Row {
+                    spacing: 8
+                    Rectangle { width: 8; height: 8; radius: 4; color: Theme.sensorLow; anchors.verticalCenter: parent.verticalCenter }
+                    Label { text: "Low"; font.pixelSize: Theme.fontXs; color: Theme.sideMutedText; anchors.verticalCenter: parent.verticalCenter }
+                }
+                Row {
+                    spacing: 8
+                    Rectangle { width: 8; height: 8; radius: 4; color: Theme.sensorInRange; anchors.verticalCenter: parent.verticalCenter }
+                    Label { text: "In-range"; font.pixelSize: Theme.fontXs; color: Theme.sideMutedText; anchors.verticalCenter: parent.verticalCenter }
+                }
+                Row {
+                    spacing: 8
+                    Rectangle { width: 8; height: 8; radius: 4; color: Theme.sensorHigh; anchors.verticalCenter: parent.verticalCenter }
+                    Label { text: "High"; font.pixelSize: Theme.fontXs; color: Theme.sideMutedText; anchors.verticalCenter: parent.verticalCenter }
+                }
+            }
+
+            Rectangle {
+                Layout.preferredWidth: Theme.borderThin
+                Layout.preferredHeight: 14
+                Layout.alignment: Qt.AlignVCenter
+                color: Theme.sideBorder
+            }
+
+            Label {
+                text: (streamController.thresholdAuto ? "Auto · " : "Manual · ")
+                    + streamController.target.toFixed(1) + " ± " + streamController.margin.toFixed(1) + "°C"
+                font.pixelSize: Theme.fontXs
+                color: Theme.headingColor
+            }
+        }
+    }
+
     function exportImage(filePath, extra) {
         return map.export_image(filePath, extra || "");
     }

src/pygui/backend/controllers/session_controller.py

@@ -182,6 +182,11 @@ class SessionController(QObject):
         """Resolved band half-width (frame 1σ in auto mode, else margin)."""
         return self._last.margin if self._last else 1.0
 
+    @Property(bool, notify=frameUpdated)
+    def thresholdAuto(self) -> bool:
+        """Whether the current band is auto-derived (frame mean ± 1σ) or manual."""
+        return self._model.auto
+
     @Property(dict, notify=frameUpdated)
     def stats(self) -> dict:
         if not self._last:

src/pygui/backend/models/session_model.py

@@ -26,6 +26,10 @@ class SessionModel:
     def set_thresholds(self, config: ThresholdConfig) -> None:
         self._config = config
 
+    @property
+    def auto(self) -> bool:
+        return self._config.auto
+
     def reset(self) -> None:
         self._stability.reset()