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

docs/modernization/tasks.md

@@ -591,6 +591,10 @@ Progress Notes:
 - 2026-06-13: `Canvas::stroke_draw_mix()` now routes retained mix-pass request
   wiring through `make_legacy_canvas_stroke_mix_pass_request(...)`; the legacy
   path still owns the concrete framebuffer setup and per-plane GL callbacks.
+- 2026-06-13: `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: `Canvas::stroke_draw()` live-pass sampler wiring now reuses a
   retained helper builder, and the stroke execution tests cover it. `STR-004`
   is now done after the final pad-destination helper extraction and tracker