shared-y: final review fixes

docs/claude/build-and-run.md

@@ -303,6 +303,7 @@ The cells of a figure row can **share one y range**, symmetric to the x link
   share the rest by the existing `floor + extra * w / total` rule, the floors applying to plot widths.
   Equal weights give equal plot areas; the first cell's rect is gutter plus its plot width and the rects
   still tile the row exactly.
+
 In the GTK4 and GLFW adapters the pointer is routed by **cell rect** (`row_in(rows, x, y)`: the
 containing cell, else the nearest by squared distance), one `input::Controller` per plot. The tests are
 the `figure_cell*` cases in `tests/test_figure.cpp` and `glfw_host_routes_by_cell`.