viewer: keep plot axis labels readable when compressed

When the plot dock was short, Qt Charts dropped the axis labels first, making
the plot hard to read.

- Reclaim Qt Charts' outer graphics-layout padding and trim the inner margins
  (both chart views) so the plot and its labels get the available space.
- Raise the chart minimum height (dataset-info 80 -> 140, per-image 120 -> 140)
  so the dock can't be squeezed below the point where the axis labels fit.

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

viewer/JFJochViewerDatasetInfo.cpp

@@ -52,7 +52,7 @@ JFJochViewerDatasetInfo::JFJochViewerDatasetInfo(QWidget *parent) : QWidget(pare
 
     stack = new QStackedWidget(this);
     chart_view = new JFJochDatasetInfoChartView(this);
-    chart_view->setMinimumHeight(80);   // low floor so the bottom dock resizes freely (default is set via resizeDocks)
+    chart_view->setMinimumHeight(140);   // keep enough room for the axis labels even when compressed
     grid_scan_image = new JFJochGridScanImage(this);
     image_chart = new JFJochViewerSidePanelChart(this);   // per-image profiles, folded in from the side panel
 

viewer/charts/JFJochDatasetInfoChartView.cpp

@@ -6,12 +6,18 @@
 #include <QClipboard>
 #include <QCategoryAxis>
 #include <QtCharts/QLegendMarker>
+#include <QGraphicsLayout>
 
 #include "JFJochDatasetInfoChartView.h"
 
 JFJochDatasetInfoChartView::JFJochDatasetInfoChartView(QWidget *parent)
     : QChartView(new QChart(), parent) {
     chart()->legend()->hide();
+    // Reclaim Qt Charts' outer layout padding and trim the inner margins so the axis labels keep
+    // their room even when the dock is short (otherwise they are the first thing Qt drops).
+    chart()->layout()->setContentsMargins(0, 0, 0, 0);
+    chart()->setMargins(QMargins(2, 2, 6, 2));
+    chart()->setBackgroundRoundness(0);
     setRenderHint(QPainter::Antialiasing);
    // setRubberBand(QChartView::RubberBand::RectangleRubberBand);
     setMouseTracking(true);

viewer/charts/JFJochSimpleChartView.cpp

@@ -8,11 +8,14 @@
 #include <QApplication>
 #include <QCategoryAxis>
 #include <QRegularExpression>
+#include <QGraphicsLayout>
 
 JFJochSimpleChartView::JFJochSimpleChartView(QWidget *parent)
     : QChartView(new QChart(), parent) {
     chart()->legend()->hide();
-    setMinimumHeight(120);   // soft floor: let the host dock/window decide the height
+    chart()->layout()->setContentsMargins(0, 0, 0, 0);   // reclaim padding for the plot + labels
+    chart()->setMargins(QMargins(2, 2, 6, 2));
+    setMinimumHeight(140);   // soft floor: enough for the axis labels to stay readable
     setRenderHint(QPainter::Antialiasing);
     setMouseTracking(true);
     //setRubberBand(QChartView::RubberBand::HorizontalRubberBand);