Record STR-052 closeout hash

docs/modernization/debt.md

@@ -18,6 +18,10 @@ agent or engineer to remove them without reconstructing context from chat.
 
 ## Recent Reductions
 
+- 2026-06-14: `DEBT-0036` was narrowed again. `execute_canvas_draw_merge_plane_iteration()`
+  now routes the per-plane dispatch wrapper through
+  `execute_canvas_draw_merge_plane_dispatch(...)`; the plane loop still owns
+  the plane-selection guard and helper dispatch.
 - 2026-06-14: `DEBT-0036` was narrowed again. `execute_canvas_draw_merge_branch_body()`
   now routes the branch dispatch object assembly through
   `make_canvas_draw_merge_branch_dispatch(...)`; the branch body still owns the