probes: print cells and column weights; split-row ruler label

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

src/ui_app.hpp

@@ -2112,6 +2112,11 @@ GtkWidget* layout_cell_button(App& a, int fr, int pos);
 GtkWidget* layout_col_handle(App& a, int plot);
 void layout_col_apply(App& app, int plot, double offset_px);
 void layout_probe_report(App& a, const char* what);
+/// The split in the report lines, from the `RowSet` alone (no widget is asked, so the exit dump can
+/// use them): cells per figure row (`1,2,1`) and each figure row's cell weights, rows divided by `|`
+/// and empty for an unsplit row (`|0.3,0.7|`).
+std::string layout_cells_text(const RowSet& rs);
+std::string layout_colweights_text(const RowSet& rs);
 void layout_click(GtkWidget* b);
 void layout_probe_next(App& a, int step, guint delay_ms);
 gboolean layout_probe_step(gpointer user);