figure: shared-y rows draw one y axis, on the first cell

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/render/renderer.cpp

@@ -902,9 +902,14 @@ void Renderer::draw_tick_labels(const Plot& plot, const PlotLayout& layout) {
   // Y labels: right-aligned in their strip, centred on the tick and pulled back
   // inside the strip at the two extremes (a label centred on the top tick would
   // otherwise hang above the plot area).
+  //
+  // Unless the plot gave its y strip away (`YStrip::None`, a later cell of a split row that
+  // shares one y axis): its label area is then zero wide, and labels right-aligned against it
+  // would be drawn in the neighbouring cell. Keyed on the area rather than the mode so a strip
+  // the layout clamped to nothing stages nothing either.
   const f32 top_limit =
       std::max(layout.y_label_area.y, layout.y_label_area.bottom() - line_h);
-  for (u32 i = 0; i < plot.y_axis_count(); ++i) {
+  for (u32 i = 0; layout.y_label_area.w > 0.0f && i < plot.y_axis_count(); ++i) {
     const Transform transform = plot.y_transform(i);
     for (const Tick& tick : plot.y_axis(i).ticks) {
       if (!tick.major || tick.label.empty()) continue;