viewer: per-image plot reuses the dataset-info combo (no second combo)

In per-image mode the embedded chart brought its own combo box, so the plot
panel showed two. Drop the per-image chart's combo and drive it from the one
dataset-info combo:

- JFJochViewerSidePanelChart loses its combo; it exposes PlotTypes() (the
  available profiles) and a setPlotType(code) slot, driven externally.
- JFJochViewerDatasetInfo fills its single combo with the per-image plot types
  while in per-image mode (per-dataset metrics otherwise) and routes the
  selection to the chart; dataset/runs/live updates leave the per-image combo
  and plot untouched.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

viewer/JFJochViewerDatasetInfo.cpp

@@ -105,7 +105,9 @@ JFJochViewerDatasetInfo::JFJochViewerDatasetInfo(QWidget *parent) : QWidget(pare
             [this]() {
                 if (image_button->isChecked())
                     grid_button->setChecked(false);
-                combo_box->setEnabled(!image_button->isChecked());   // the metric combo is for the dataset plot
+                UpdateLabels();                  // swap the one combo's contents for the mode
+                combo_box->setCurrentIndex(0);
+                comboBoxSelected(0);             // apply the first option of the new mode
                 UpdateView();
             });
     connect(image_chart, &JFJochViewerSidePanelChart::writeStatusBar,
@@ -121,6 +123,13 @@ void JFJochViewerDatasetInfo::UpdateLabels() {
 
     combo_box->clear();
 
+    // In per-image mode the one combo selects which per-image profile to show (no second combo).
+    if (image_button && image_button->isChecked()) {
+        for (const auto &pt : JFJochViewerSidePanelChart::PlotTypes())
+            combo_box->addItem(pt.first, pt.second);
+        return;
+    }
+
     if (this->dataset) {
         combo_box->addItem("Background estimate", 0);
         combo_box->addItem("Resolution estimate", 7);
@@ -173,6 +182,12 @@ void JFJochViewerDatasetInfo::UpdateLabels() {
 
 void JFJochViewerDatasetInfo::datasetLoaded(std::shared_ptr<const JFJochReaderDataset> dataset) {
     this->dataset = dataset;
+    // Per-image mode: the combo holds plot types and the chart follows the displayed image, so a
+    // new dataset must not repopulate the combo or run the per-dataset plot.
+    if (image_button && image_button->isChecked()) {
+        UpdateView();
+        return;
+    }
     if (dataset) {
         UpdateLabels();
         if (last_selection < combo_box->count())
@@ -312,6 +327,8 @@ void JFJochViewerDatasetInfo::UpdateView() {
 void JFJochViewerDatasetInfo::runsChanged(QVector<RunData> runs, QString active_id) {
     runs_ = std::move(runs);
     active_id_ = std::move(active_id);
+    if (image_button && image_button->isChecked())
+        return;   // per-image mode: runs/overlays are a per-dataset concern
     UpdateLabels();
     if (last_selection < combo_box->count())
         combo_box->setCurrentIndex(last_selection);
@@ -320,11 +337,19 @@ void JFJochViewerDatasetInfo::runsChanged(QVector<RunData> runs, QString active_
 
 void JFJochViewerDatasetInfo::liveRunUpdated(std::shared_ptr<const JFJochReaderDataset> in_dataset) {
     live_run_ = std::move(in_dataset);
+    if (image_button && image_button->isChecked())
+        return;
     UpdatePlot();   // lightweight refresh; no combo rebuild on every live tick
 }
 
 void JFJochViewerDatasetInfo::comboBoxSelected(int index) {
-    UpdatePlot();
+    // The one combo means per-dataset metrics in normal mode, per-image plot types in image mode.
+    if (image_button && image_button->isChecked()) {
+        if (image_chart && index >= 0 && index < combo_box->count())
+            image_chart->setPlotType(combo_box->itemData(index).toInt());
+    } else {
+        UpdatePlot();
+    }
 }
 
 void JFJochViewerDatasetInfo::setColorMap(int color_map) {