Extend retained stroke helper dispatch tests

docs/modernization/roadmap.md

@@ -3127,6 +3127,9 @@ Results:
   input binding order, sample execution destination-copy behavior, live-pass
   face-framebuffer dirty tracking, and pad-face destination-copy behavior
   without depending on the broader compositor test translation unit.
+- `pp_paint_renderer_stroke_execution_tests` now also covers retained texture
+  dispatch activation order and sampler-dispatch routing across brush tip,
+  destination, pattern, and mixer helper inputs.
 - `Canvas::stroke_draw` pad-pass destination bind/copy/unbind ordering now
   shares the retained stroke execution helper callback surface, while shader
   setup, pad color selection, framebuffer ownership, and final OpenGL draw