Share retained erase temporary composite helper

docs/modernization/debt.md

@@ -18,6 +18,11 @@ agent or engineer to remove them without reconstructing context from chat.
 
 ## Recent Reductions
 
+- 2026-06-13: DEBT-0036 was narrowed again. `Canvas::draw_merge()` erase live
+  temporary-stroke composite now routes retained setup, sampler bind, texture
+  bind, draw, and texture unbind ordering through
+  `execute_legacy_canvas_stroke_temporary_composite(...)`; broader final
+  composite ownership remains in the legacy Canvas path.
 - 2026-06-13: DEBT-0036 was narrowed again. `NodeStrokePreview::stroke_draw_mix()`
   now routes retained mix-pass shader setup plus framebuffer/state/input/draw
   ordering through `execute_legacy_node_stroke_preview_mix_pass(...)`; the