Trim stroke mix execution shell

docs/modernization/debt.md

@@ -18,6 +18,11 @@ agent or engineer to remove them without reconstructing context from chat.
 
 ## Recent Reductions
 
+- 2026-06-13: `LATER-003` was narrowed again. `Canvas::stroke_draw_mix()` now
+  routes its retained mix-pass execution shell through
+  `execute_legacy_canvas_stroke_mix_pass_with_setup(...)` with a concrete
+  request builder; the live path still owns the OpenGL setup and per-plane
+  texture wiring.
 - 2026-06-13: `LATER-003` was narrowed again. `Canvas::stroke_draw_mix()` now
   routes retained mix-pass request wiring through
   `make_legacy_canvas_stroke_mix_pass_request(...)`; the legacy path still