Promote STR-009 stroke commit task

docs/modernization/tasks.md

@@ -986,3 +986,33 @@ ctest --preset desktop-fast --build-config Debug -R "pp_paint_renderer_stroke_ex
 | Date | Task | Score | Validation | Commit |
 | --- | --- | ---: | --- | --- |
 | 2026-06-13 | STR-008 | +1 renderer boundary and OpenGL parity | `ctest --preset desktop-fast --build-config Debug -R "pp_paint_renderer_stroke_execution" --output-on-failure`; `MSBuild.exe out\build\windows-msvc-default\tests\pp_paint_renderer_stroke_execution_tests.vcxproj /p:Configuration=Debug /p:Platform=x64` | `11a62e9b` |
+
+### STR-009 - Extract Stroke Commit Callback Orchestration
+
+Status: Ready
+Score: +2 renderer boundary and OpenGL parity
+Debt: `DEBT-0036`
+Scope: `src/canvas.cpp`, `src/legacy_canvas_stroke_execution_services.h`,
+`tests/paint_renderer/stroke_execution_tests.cpp`
+
+Goal:
+
+Move the large inline callback block in `Canvas::stroke_commit()` into a
+retained helper so commit sequencing keeps only concrete layer/texture/canvas
+wiring. Preserve commit ordering, history capture, and dilate sequencing.
+
+Done Checks:
+
+- `Canvas::stroke_commit()` no longer contains the large inline commit callback
+  block around `execute_legacy_canvas_stroke_commit_sequence(...)`.
+- Regression coverage proves the extracted helper preserves commit ordering and
+  history capture.
+- `docs/modernization/debt.md` records the reduced stroke-commit callback
+  surface.
+
+Validation:
+
+```powershell
+ctest --preset desktop-fast --build-config Debug -R "pp_paint_renderer_stroke_execution" --output-on-failure
+& 'C:\Program Files\Microsoft Visual Studio\18\Community\MSBuild\Current\Bin\MSBuild.exe' out\build\windows-msvc-default\tests\pp_paint_renderer_stroke_execution_tests.vcxproj /p:Configuration=Debug /p:Platform=x64
+```