Promote stroke commit service boundary task

docs/modernization/tasks.md

@@ -1806,6 +1806,35 @@ ctest --preset desktop-fast --build-config Debug -R "pp_paint_renderer_composito
 cmake --build --preset windows-msvc-default --config Debug --target PanoPainter
 ```
 
+### STR-039 - Wire Stroke Commit Service Boundary
+
+Status: Ready
+Score: +1 renderer boundary and OpenGL parity
+Debt: `DEBT-0036`
+Scope: `src/canvas.cpp`, `src/legacy_canvas_stroke_commit_services.h`, `tests/paint_renderer/stroke_execution_tests.cpp`
+
+Goal:
+
+Move the remaining `Canvas::stroke_commit()` service wiring behind the retained
+stroke-commit helper boundary so the callsite keeps only local history and
+layer mutation logic.
+
+Done Checks:
+
+- `Canvas::stroke_commit()` no longer owns the retained commit-service wiring
+  inline.
+- Regression coverage proves the helper preserves commit ordering and history
+  capture.
+- `docs/modernization/debt.md` records the reduced stroke-commit service
+  surface.
+
+Validation:
+
+```powershell
+ctest --preset desktop-fast --build-config Debug -R "pp_paint_renderer_stroke_execution" --output-onfailure
+& '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
+```
+
 ### STR-010 - Extract Remaining Draw Merge Composite Orchestration
 
 ### STR-016 - Extract Draw Merge Layer Composite Execution