Share retained stroke temporary composite helper

docs/modernization/debt.md

@@ -38,6 +38,11 @@ agent or engineer to remove them without reconstructing context from chat.
   through `execute_legacy_canvas_stroke_face_sample_polygon(...)`; the
   retained sample executor owns the face-aware dispatch contract while
   `Canvas` keeps only concrete GL object callbacks.
+- 2026-06-13: DEBT-0036 was narrowed again. `Canvas::draw_merge()` non-erase
+  live temporary-stroke composite now routes setup, sampler bind, texture
+  bind, draw, and texture unbind ordering through
+  `execute_legacy_canvas_stroke_temporary_composite(...)`; erase-path and
+  broader final composite ownership remain retained in `Canvas`.
 - 2026-06-13: DEBT-0036 was narrowed again. `NodeStrokePreview::stroke_draw_mix()`
   now routes mixer framebuffer bind/unbind, viewport/scissor/blend state,
   texture-slot binding, and final plane draw through one local helper;

docs/modernization/roadmap.md

@@ -3137,6 +3137,10 @@ Results:
   `execute_legacy_canvas_stroke_face_sample_polygon(...)` for face-indexed
   destination bind/copy/unbind and brush upload/draw dispatch, while concrete
   GL object callbacks remain in the legacy Canvas path.
+- `Canvas::draw_merge()` non-erase live temporary-stroke composite now shares
+  `execute_legacy_canvas_stroke_temporary_composite(...)` for setup, sampler
+  bind, texture bind, draw, and texture unbind ordering, while erase-path and
+  broader final composite ownership remain in the legacy Canvas path.
 - `NodeStrokePreview::stroke_draw_mix()` now shares one local helper for mixer
   framebuffer bind/unbind, viewport/scissor/blend state, texture-slot
   binding, and final plane draw, while material planning and shader uniform

docs/modernization/tasks.md

@@ -509,6 +509,13 @@ Done Checks:
 
 Progress Notes:
 
+- 2026-06-13: `Canvas::draw_merge()` non-erase live temporary-stroke
+  composite ordering now routes through
+  `execute_legacy_canvas_stroke_temporary_composite(...)`; erase-path and
+  broader final composite ownership still remain local to `Canvas`. Next slice
+  should target the erase temporary composite branch or another similarly
+  narrow final composite seam without reopening landed sample, mix, dirty, or
+  framebuffer helpers.
 - 2026-06-13: `Canvas::stroke_draw_samples()` now routes face-indexed
   destination bind/copy/unbind and brush upload/draw through
   `execute_legacy_canvas_stroke_face_sample_polygon(...)`; the retained sample