feat(map): add min/max highlighting toggle and live safeguards

- Add "Highlight Min/Max" option to ReadoutPanel showing peak rings.
- Reset to review mode and blank wafer map when switching away from map tab.
- Disable hover highlights and sensor dialog triggers during live stream.
- Lower trendPane height and add top margin headroom for tick labels.
- Add test coverage for blanking states, toggle overrides, and interactions.

src/pygui/backend/controllers/session_controller.py

@@ -225,6 +225,12 @@ class SessionController(QObject):
             return
         if mode != "live":
             self.stopStream()
+            if self._mode == "live":
+                # Leaving a live session: blank the wafer map instead of
+                # freezing the last streamed frame on screen.
+                self._last = None
+                self._last_raw_frame = None
+                self.frameUpdated.emit()
         self._play_timer.stop()
         self._mode = mode
         self.modeChanged.emit()

src/pygui/backend/visualization/trend_chart_item.py

@@ -58,6 +58,9 @@ class TrendChartItem(QQuickPaintedItem):
         # `_padding` alone — that mismatch is what clipped y-axis text before.
         self._margin_left: int = 48
         self._margin_bottom: int = 30
+        # Top tick label is drawn centered on the plot's top edge (y_px - 7),
+        # so the plot needs headroom or the label kisses the card border.
+        self._margin_top: int = 10
         self._line_color = QColor("#5B9DF5")
         self._grid_color = QColor("#2A3441")
         self._text_color = QColor("#CBD5E1")
@@ -178,10 +181,11 @@ class TrendChartItem(QQuickPaintedItem):
             return
 
         left = self._padding + self._margin_left
+        top = self._padding + self._margin_top
         bottom_inset = self._padding + self._margin_bottom
-        plot_rect = QRectF(left, self._padding,
+        plot_rect = QRectF(left, top,
                            max(1, w - left - self._padding),
-                           max(1, h - self._padding - bottom_inset))
+                           max(1, h - top - bottom_inset))
 
         self._draw_grid(painter, plot_rect)
 

src/pygui/backend/visualization/wafer_map_item.py

@@ -62,6 +62,7 @@ class WaferMapItem(QQuickPaintedItem):
     marginChanged   = Signal()
     blendChanged    = Signal()
     showLabelsChanged = Signal()
+    showExtremesChanged = Signal()
     colorsChanged   = Signal()
     shapeChanged    = Signal()
     sizeChanged     = Signal()
@@ -80,6 +81,7 @@ class WaferMapItem(QQuickPaintedItem):
         self._margin:   float = 1.0
         self._blend:    float = 0.0
         self._show_labels: bool = True
+        self._show_extremes: bool = True
         self._shape: str = "round"
         self._size: float = 300.0
         self._thickness_data: list[float] = []
@@ -199,6 +201,16 @@ class WaferMapItem(QQuickPaintedItem):
         self.showLabelsChanged.emit()
         self.update()
 
+    @Property(bool, notify=showExtremesChanged)
+    def showExtremes(self) -> bool:
+        return self._show_extremes
+
+    @showExtremes.setter  # type: ignore[no-redef]
+    def showExtremes(self, val: bool) -> None:
+        self._show_extremes = bool(val)
+        self.showExtremesChanged.emit()
+        self.update()
+
     @Property(str, notify=shapeChanged)
     def shape(self) -> str:
         return self._shape
@@ -340,7 +352,6 @@ class WaferMapItem(QQuickPaintedItem):
             img.fill(0)  # transparent background
             painter = QPainter(img)
             self.paint(painter)
-            self._paint_extremes(painter)
             if lines:
                 painter.fillRect(QRectF(0, h, w, footer_h), QColor("#101014"))
                 painter.setPen(QColor("#CBD5E1"))
@@ -357,12 +368,8 @@ class WaferMapItem(QQuickPaintedItem):
     # ── internal ─────────────────────────────────────────────────────────
 
     def _paint_extremes(self, painter: QPainter) -> None:
-        """Ring the hottest (high color) and coldest (low color) markers.
-
-        Export-only overlay — paint() itself stays untouched so the live
-        view is unchanged.
-        """
-        if not self._values or not self._markers:
+        """Ring the hottest (high color) and coldest (low color) markers."""
+        if not self._show_extremes or not self._values or not self._markers:
             return
         s = compute_stats(self._values)
         ring_r = self._marker_r + 5
@@ -606,6 +613,7 @@ class WaferMapItem(QQuickPaintedItem):
             painter.setOpacity(1.0)
 
         self._paint_markers(painter)
+        self._paint_extremes(painter)
 
     def _paint_template(self, painter: QPainter, cx: int, cy: int, r_px: int) -> None:
         ds = self._draw_size()