Share retained stroke sample and mix helpers

docs/modernization/debt.md

@@ -23,6 +23,16 @@ agent or engineer to remove them without reconstructing context from chat.
   retained stroke execution helpers; concrete GL object mapping, framebuffer
   ownership, shader timing, and final draw execution remain retained in
   `Canvas`.
+- 2026-06-13: DEBT-0036 was narrowed again. `Canvas::stroke_draw_samples()`
+  now routes polygon triangulation, sample-point assembly, and retained
+  destination-copy / upload / draw helper handoff through
+  `execute_legacy_canvas_stroke_sample_polygon(...)`; direct GL callback
+  wiring and remaining live draw ownership remain retained in `Canvas`.
+- 2026-06-13: DEBT-0036 was narrowed again. `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 retained in the preview
+  node.
 - 2026-06-13: DEBT-0036 was narrowed again. `NodeStrokePreview::stroke_draw_samples`
   now routes destination bind/unbind, framebuffer copy callback wrapping,
   sample-point assembly, and brush-vertex upload/draw through one local helper;