Share retained stroke sample and mix helpers

docs/modernization/tasks.md

@@ -509,6 +509,20 @@ Done Checks:
 
 Progress Notes:
 
+- 2026-06-13: `Canvas::stroke_draw_samples()` now routes polygon
+  triangulation, sample-point assembly, and the retained destination-copy /
+  upload / draw helper handoff through
+  `execute_legacy_canvas_stroke_sample_polygon(...)`; direct GL callback
+  wiring and the remaining live draw ownership stay local to `Canvas`. Next
+  slice should target the remaining callback body or final temporary-texture
+  composite setup without reopening the landed sampler, dirty, face, or pad
+  helpers.
+- 2026-06-13: `NodeStrokePreview::stroke_draw_mix()` now routes mixer
+  framebuffer bind/unbind, viewport/scissor/blend state, texture-slot binding,
+  and final plane draw through one local helper; material planning and shader
+  uniform setup remain local to the preview node. Next slice should target the
+  remaining mix-pass material/setup orchestration without reopening the landed
+  preview live-pass, binding, sample, or final composite helpers.
 - 2026-06-13: `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. Next test