feat: a repaired invalid span is shaded faintly, not solidly

include/plot/render/renderer.hpp

@@ -513,10 +513,11 @@ class Renderer {
   void draw_plot(Plot& plot, const PlotLayout& layout);
 
   void draw_grid(const Plot& plot);
-  /// `Plot::invalid_spans()`, as `PlotLayout::invalid_spans` measured them: one fill per span in
-  /// `style_.invalid_fill`. Over the grid and under everything else inside the axes, so a hole
-  /// reads as a property of the plot's background -- the grid shows through it and a trace that
-  /// does have data in those columns is drawn on top, which is what distinguishes a reserved
+  /// `Plot::invalid_spans()`, as `PlotLayout::invalid_spans` measured them: one fill per span,
+  /// in `style_.invalid_fill` or — for a span the host has marked repaired —
+  /// `style_.invalid_repaired_fill`. Over the grid and under everything else inside the axes, so
+  /// a hole reads as a property of the plot's background -- the grid shows through it and a trace
+  /// that does have data in those columns is drawn on top, which is what distinguishes a reserved
   /// hole from a trace that has gone quiet.
   void draw_invalid_spans(const PlotLayout& layout);
   void draw_axis_lines(const Plot& plot);