Extract stroke commit history mutation helpers

docs/modernization/debt.md

@@ -182,6 +182,10 @@ agent or engineer to remove them without reconstructing context from chat.
   routes the remaining service wiring through `make_canvas_stroke_commit_request(...)`;
   the retained path still owns the concrete history mutation and layer dirty
   box updates.
+- 2026-06-13: DEBT-0036 was narrowed again. `Canvas::stroke_commit()` now
+  routes action bookkeeping and dirty-box capture/mutation through helper
+  functions; the retained callback builder now only forwards concrete canvas
+  state.
 - 2026-06-13: DEBT-0036 was narrowed again. `Canvas::stroke_commit()` now
   builds its retained callback table through
   `make_legacy_canvas_stroke_commit_callbacks(...)`; the legacy executor still

docs/modernization/tasks.md

@@ -1839,7 +1839,7 @@ ctest --preset desktop-fast --build-config Debug -R "pp_paint_renderer_stroke_ex
 
 ### STR-040 - Extract Stroke Commit Local History And Dirty Mutation
 
-Status: Ready
+Status: Done
 Score: +1 renderer boundary and OpenGL parity
 Debt: `DEBT-0036`
 Scope: `src/canvas.cpp`, `tests/paint_renderer/stroke_execution_tests.cpp`
@@ -1850,6 +1850,8 @@ Move the remaining local history and dirty-mutation work inside
 `make_canvas_stroke_commit_callbacks()` into a retained helper so the callback
 builder only forwards concrete canvas state.
 
+Closeout: `aa53a5f9`
+
 Done Checks:
 
 - `make_canvas_stroke_commit_callbacks()` no longer owns the history/dirty