Promote remaining draw merge branch task

docs/modernization/tasks.md

@@ -1855,6 +1855,35 @@ ctest --preset desktop-fast --build-config Debug -R "pp_paint_renderer_composito
 | --- | --- | ---: | --- | --- |
 | 2026-06-13 | STR-031 | +1 renderer boundary and OpenGL parity | `ctest --preset desktop-fast --build-config Debug -R "pp_paint_renderer_compositor|pp_paint_renderer_stroke_execution" --output-onfailure` | `91d4da09` |
 
+### STR-032 - Extract Remaining Draw Merge Branch Orchestration
+
+Status: Ready
+Score: +2 renderer boundary and OpenGL parity
+Debt: `DEBT-0036`
+Scope: `src/canvas.cpp`, `src/legacy_canvas_draw_merge_services.*`, `tests/paint_renderer/compositor_tests.cpp`
+
+Goal:
+
+Move the remaining inline `Canvas::draw_merge()` branch orchestration into
+retained helpers so the merge path keeps only concrete framebuffer, sampler,
+and texture wiring. Preserve per-plane order, temporary-stroke behavior, and
+final merge composition.
+
+Done Checks:
+
+- `Canvas::draw_merge()` no longer contains the remaining large inline branch
+  orchestration for temporary-stroke or blend/final-plane composition.
+- Regression coverage proves the extracted helper preserves ordering and
+  branch behavior.
+- `docs/modernization/debt.md` records the reduced draw-merge callback surface.
+
+Validation:
+
+```powershell
+ctest --preset desktop-fast --build-config Debug -R "pp_paint_renderer_compositor" --output-onfailure
+& 'C:\Program Files\Microsoft Visual Studio\18\Community\MSBuild\Current\Bin\MSBuild.exe' out\build\windows-msvc-default\tests\pp_paint_renderer_compositor_tests.vcxproj /p:Configuration=Debug /p:Platform=x64
+```
+
 ### STR-012 - Extract Preview Final Composite Orchestration
 
 Status: Done