fix: replace corr() with corrcoef() in example_widget_scatter

corr() requires the Statistics Toolbox which isn't available in the
MATLAB CI runner. corrcoef() is a built-in that works without toolboxes.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: HanSur94

examples/example_widget_scatter.m

@@ -101,7 +101,8 @@
 %% 3. Render
 d.render();
 fprintf('Dashboard rendered with %d scatter widgets.\n', numel(d.Widgets));
-fprintf('Correlation T-P: %.2f  T-F: %.2f  P-F: %.2f\n', ...
-    corr(sTemp.Y(:), sPress.Y(:)), ...
-    corr(sTemp.Y(:), sFlow.Y(:)), ...
-    corr(sPress.Y(:), sFlow.Y(:)));
+% Pearson correlation (toolbox-free)
+r_tp = corrcoef(sTemp.Y(:), sPress.Y(:)); r_tp = r_tp(1,2);
+r_tf = corrcoef(sTemp.Y(:), sFlow.Y(:));  r_tf = r_tf(1,2);
+r_pf = corrcoef(sPress.Y(:), sFlow.Y(:)); r_pf = r_pf(1,2);
+fprintf('Correlation T-P: %.2f  T-F: %.2f  P-F: %.2f\n', r_tp, r_tf, r_pf);