Move stroke commit request assembly behind service helper

docs/modernization/debt.md

@@ -115,6 +115,10 @@ agent or engineer to remove them without reconstructing context from chat.
 - 2026-06-13: `DEBT-0036` was narrowed again. `Canvas::stroke_commit()`
   now routes the face-indexed commit-input binding wrapper through the retained
   service boundary, leaving `Canvas` with only concrete face bindings.
+- 2026-06-13: `DEBT-0036` was narrowed again. `Canvas::stroke_commit()`
+  now routes the retained commit request assembly through
+  `make_legacy_canvas_stroke_commit_request(...)`, leaving the callsite with
+  only concrete faces, sequence, and callbacks.
 - 2026-06-13: `DEBT-0036` was narrowed again. `NodeStrokePreview::draw_stroke_immediate()`
   now routes final composite execution and preview copy-back through a retained
   local wrapper, leaving the call site with only sequence wiring.

docs/modernization/tasks.md

@@ -1253,6 +1253,10 @@ ctest --preset desktop-fast --build-config Debug -R "pp_paint_renderer_stroke_ex
 | --- | --- | ---: | --- | --- |
 | 2026-06-13 | STR-014 | +1 renderer boundary and OpenGL parity | `ctest --preset desktop-fast --build-config Debug -R "pp_paint_renderer_stroke_execution|pp_paint_renderer_compositor" --output-on-failure` | `536f2683` |
 
+- 2026-06-13: `Canvas::stroke_commit()` now routes the retained commit request
+  assembly through `make_legacy_canvas_stroke_commit_request(...)`, so the
+  callsite only supplies concrete faces, sequence, and callbacks.
+
 ### STR-011 - Extract Preview Main Pass Orchestration
 
 Status: Done