Reduce draw merge branch dispatch mismatch

docs/modernization/debt.md

@@ -409,6 +409,10 @@ agent or engineer to remove them without reconstructing context from chat.
   now drops the unused `draw_checkerboard` parameter from the temporary-paint
   wrapper, shrinking the remaining draw-merge helper mismatch while the
   blocked extraction still stays in `STR-016`.
+- 2026-06-15: `DEBT-0036` was narrowed again. The stale
+  `make_canvas_draw_merge_branch_dispatch(...)` forward declaration in
+  `src/canvas.cpp` now matches the 7-argument implementation, shrinking the
+  remaining draw-merge helper API mismatch while `STR-016` stays blocked.
 - 2026-06-14: `DEBT-0036` was narrowed again. `Canvas::draw_merge_branch_orchestration()`
   now routes the temporary erase, temporary paint, texture, and blend dispatch
   bodies through retained helpers inside `execute_canvas_draw_merge_branch_body(...)`;

docs/modernization/roadmap.md

@@ -77,6 +77,9 @@ The same checked-overlay seam now also owns main-toolbar settings dialog
 opening from `src/legacy_app_shell_services.cpp`, removing another raw
 app-owned dialog insertion path while leaving the remaining retained dialog
 families debt-tracked.
+The stale `make_canvas_draw_merge_branch_dispatch(...)` forward declaration in
+`src/canvas.cpp` now matches the existing 7-argument implementation, shrinking
+the remaining draw-merge helper API mismatch while `STR-016` stays blocked.
 The cloud browser dialog now also opens through that seam from
 `src/legacy_cloud_services.cpp`, so the remaining cloud modernization debt is
 now concentrated in retained background worker threads, transfer helpers,

src/canvas.cpp

@@ -591,8 +591,7 @@ static pp::panopainter::LegacyCanvasDrawMergeLayerCompositeExecution make_canvas
     const std::shared_ptr<Layer>& layer,
     const Brush& brush,
     const glm::mat4& ortho,
-    bool copy_blend_destination,
+    bool copy_blend_destination);
-    bool draw_checkerboard);
 
 static void execute_canvas_draw_merge_branch_body(
     Canvas& canvas,